David Letterman, host of Late Show, plans to retire in 2015

David Letterman is retiring next year as host of Late Show.

During a taping of Thursday's show, Letterman said he has informed CBS that he will step down in 2015, when his current contract expires.

He announced no specific end date, telling his audience he expects his exit will be in "at least a year or so, but sometime in the not too distant future 2015, for the love of God, (band leader) Paul (Shaffer) and I will be wrapping things up."

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What he'll be wrapping up is three decades on the air the longest tenure of any late-night talk show host in U.S. television history since he launched Late Nightat NBC in 1982.

But more than that, he'll be ending a lineage of late-night hosts who pioneered talk and humor in the wee hours Johnny Carson, of course, and, before him, Jack Paar and especially Steve Allen.

Ironically, they were all on NBC, the network that denied Letterman the Tonight Showcrown he sought and, after he lost out to Jay Leno, prompted him to pitch his tent at CBS as Leno's rival.

'The network has been great but i'm retiring'

Referring to CBS chairman Leslie Moonves as "the man who owns this network," Letterman told viewers Thursday, "I phoned him just before the program, and I said, `Leslie, it's been great, you've been great, and the network has been great, but I'm retiring."'

Along with his network, Letterman thanked "all of the people who have worked here, all of the people in the theater, all the people on the staff, everybody at home thank you very much.

"What this means now," he cracked, "is that Paul and I can be married."

Since premiering with Late Showin 1993, Letterman, who turns 67 next week, has reigned at Broadway's Ed Sullivan Theater, a historic venue nearly a century old that was famously home to The Ed Sullivan Show.

The Los Angeles-based Leno, 63, retired from "The Tonight Show" this year, clearing the way, not by his choice, for Late Nighthost Jimmy Fallon to move up to that TV institution.

In contrast to Leno, Letterman's leave-taking appears to be his choice.

"For 21 years, David Letterman has graced our network's air in late night with wit, gravitas and brilliance unique in the history of our medium," Moonves said. "It's going to be tough to say goodbye."

Letterman, who was a radio talk show host and local TV weatherman, moved to Los Angeles in the 1970s and, among his early gigs, was a writer and performer on a summer variety show and a member of the comedy troupe of a short-lived program starring Mary Tyler Moore.

In 1980, he hosted an NBC morning show, which lasted only five months while winning two Emmy awards.

Two years after that, he was turned loose with Late Night,where he clicked.

Leno held ratings leadership

A generation later, Letterman will leave with an unparalleled comic legacy of weirdness, laser-focused sarcasm and an ironic sensibility that saturated the culture. ("Letterman-esque" may not be in any dictionary, but his fans know what it means.)

Leno held the ratings leadership for most of the two-decade duel with Letterman.

But Letterman remained the overwhelming critical favorite. He earned a Peabody Award in 1992 and a Kennedy Center Honor in 2012. Late Showwon a prime-time Emmy in 1994, one of several showered on his programs through the years.

In an interview with Howard Stern in January, Letterman declared that Leno's departure would have no impact on how much longer he might stay as "Late Show" host.

"I would do it forever if it were up to me," said Letterman, before adding a wry aside: "Sometimes, it isn't up to me."

But now, with the late-night dust settling at NBC, Who Replaces Letterman becomes the new guessing game. In the wings as a prospective heir: Craig Ferguson, host of The Late Late Show,which has followed Letterman, who produces it, since 2005.

Syndicated late-night host Arsenio Hall said Thursday that CBS might be able to fill Letterman's time slot, "but it can never fill the void he will leave behind."

ABC host Jimmy Kimmel tweeted that Letterman "is the best there is and ever was."