David Letterman arrives at the Statue Of Liberty Museum Opening Celebration at Battery Park in New York, U.S., May 15, 2019. REUTERS/Demetrius Freeman

U.S. Secretary of Veterans Affairs David Shulkin and his wife Merle Bari arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor at Kennedy Center, in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Chris Elliott and his wife Paula Niedert Elliott arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Bruce Vilanch arrives for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Announcer Alan Kalter and his wife Peggy Masterson arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Senator Al Franken, his wife Franni Bryson (L) and their daughter Thomasin arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Jimmie Walker arrives for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Psychiatrist Clarice Kestenbaum and her sons David and John Stone arrive for a gala honoring David Letterman who is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Senator Al Franken speaks to the media at a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Jimmy Kimmel speaks to the media at a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor at Kennedy Center, in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian John Mulaney speaks to the media at a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian John Mulaney and his wife Annamarie Tendler arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian John Mulaney and his wife Annamarie Tendler arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Martin Short arrives for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Martin Short arrives for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Musician Eddie Vedder and his wife Jill McCormick arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Musician Eddie Vedder and his wife Jill McCormick arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Jimmy Kimmel and his wife Molly McNearney arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Jimmy Kimmel and his wife Molly McNearney arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Jimmy Kimmel and his wife Molly McNearney arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian Jimmy Kimmel and his wife Molly McNearney arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Musician Paul Shaffer, his wife Cathy Vasapoli (R) and daughter Victoria arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Musician Paul Shaffer, his wife Cathy Vasapoli (R) and daughter Victoria arrive for a gala honoring David Letterman, who is receiving the Mark Twain Prize for American Humor, at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman speaks to the media as he arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman and his band leader Paul Shaffer speak to the media as Letterman arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman and his band leader Paul Shaffer speak to the media as Letterman arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman speaks to the media as he arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman speaks to the media as he arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman speaks to the media as he arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman greets his son Harry as he arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman greets his son Harry as he arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman greets his wife Regina Lasko as he arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman and his wife Regina Lasko arrive for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman and his wife Regina Lasko arrive for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman and his wife Regina Lasko arrive for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Comedian David Letterman arrives for a gala where he is receiving the Mark Twain Prize for American Humor at Kennedy Center in Washington, U.S., October 22, 2017. REUTERS/Joshua Roberts

Former talk show host and comedian David Letterman arrives for the 2017 Profile in Courage Award ceremony, being given to former U.S. President Barack Obama, at the John F. Kennedy Library in Boston, Massachusetts, U.S., May 7, 2017. REUTERS/Brian Snyder

Former talk show host and comedian David Letterman arrives for the 2017 Profile in Courage Award ceremony, being given to former U.S. President Barack Obama, at the John F. Kennedy Library in Boston, Massachusetts, U.S., May 7, 2017. REUTERS/Brian Snyder TPX IMAGES OF THE DAY

32nd Annual Rock & Roll Hall of Fame Induction Ceremony - Show – New York City, U.S., 07/04/2017 – Presenter David Letterman inducts Pearl Jam. REUTERS/Lucas Jackson

32nd Annual Rock & Roll Hall of Fame Induction Ceremony - Show – New York City, U.S., 07/04/2017 – Presenter David Letterman. REUTERS/Lucas Jackson

32nd Annual Rock & Roll Hall of Fame Induction Ceremony - Show – New York City, U.S., 07/04/2017 – Presenter David Letterman. REUTERS/Lucas Jackson

32nd Annual Rock & Roll Hall of Fame Induction Ceremony - Show – New York City, U.S., 07/04/2017 – David Letterman. REUTERS/Lucas Jackson

32nd Annual Rock & Roll Hall of Fame Induction Ceremony - Show – New York City, U.S., 07/04/2017 – David Letterman. REUTERS/Lucas Jackson

32nd Annual Rock & Roll Hall of Fame Induction Ceremony - Show – New York City, U.S., 07/04/2017 – David Letterman. REUTERS/Lucas Jackson

David Letterman waves to guests at the end of his speech after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman waves to guests at the end of his speech after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman speaks to guests after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman speaks to guests after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman speaks to guests after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman speaks to guests after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman speaks to guests after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman speaks to guests after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman speaks to guests after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman speaks to guests after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman speaks to guests after receiving his award at the 75th Annual Peabody Awards in New York, U.S. May 21, 2016. REUTERS/Eduardo Munoz

David Letterman and Regina Letterman arrive for the state dinner in honor of the Nordic Summit at the White House in Washington, May 13, 2016. REUTERS/Mary F. Calvert

David Letterman arrives for the state dinner in honor of the Nordic Summit at the White House in Washington, May 13, 2016. REUTERS/Mary F. Calvert