Three weeks.

That's how long it took radio giant Clear Channel Communications Inc. (CCU) to accept the third-largest buyout offer ever in the U.S., after announcing in late October that it was considering "strategic alternatives."

And while the nation's biggest radio station operator has left the door open a crack in case something better comes along, it agreed to an $18.7 billion offer from Thomas H. Lee Partners LLC and Bain Capital Partners LLC.

In addition to paying $37.60 in cash for each Clear Channel share, the buyers will assume an additional $8 billion in debt.

Chief Executive Mark Mays said the time was right to take the company private because its stock was being undervalued by equity markets.

"We tried to figure out what would be a way out of that and obviously the private equity markets have a much different view," he said by phone.

Mays said $37.60 was a "great price" for shareholders and the private equity firms "think they got a great company and have a long-term view associated with it."

The transaction would be one of the biggest deals to take a company private, excluding debt, and illustrated the vast sums that buyout specialists have been able to assemble to acquire public companies.

HCA Inc. (HCA) shareholders on Thursday overwhelmingly approved a $21.3 billion leveraged buyout — the second largest ever in the U.S. — that will take the nation's No. 1 for-profit hospital chain private. That deal is the largest since the $25.1 billion buyout of RJR Nabisco Inc. in 1988, according to Thomson Financial.

San Antonio-based Clear Channel's shares jumped $1.24, or 3.6 percent, to close at $35.36 on the New York Stock Exchange Thursday after rising earlier to a new 52-week high of $35.88.

The company has until Dec. 7 to solicit competing proposals. Another bid for Clear Channel had been expected from Providence Equity Partners, the Blackstone Group and Kohlberg Kravis Roberts & Co.

"Basically they are telling you that we have a firm offer and a firm deal, but we are not going to get locked into it yet," said Frederick Moran, a Boca Raton, Fla.-based analyst for Stanford Financial Group.

Clear Channel owns or operates 1,150 radio stations and is the largest operator of radio stations in the country.

The company said in a regulatory filing that it doesn't expect any senior management changes or significant layoffs.

Mark Mays will remain CEO while Randall Mays, his brother, will stay on as chief financial officer. Their father Lowry Mays, the chairman, will continue to have an active role, the company said. Mark Mays said Thursday that may mean a "chairman emeritus" role for his father.

"Clear Channel is an exceptional media franchise that is well-positioned to grow thanks to the solid foundation the Mays family has created," John Connaughton, a managing director at Bain Capital, said in a statement.

It's not yet clear how much the Mays stand to make in the deal. Clear Channel said Thursday that three members of senior management agreed to "significantly" reduce payments that would be made on a change of control.

A Clear Channel spokeswoman declined to elaborate. The Mays family owns about 7 percent of the company.

Mark Mays said only that "we don't stand to gain anything except what ... shareholders gain."

James Goss, media and entertainment analyst for Barrington Research, said the price of $37.60 was in line with expectations. The figure represents a 10.2 percent premium over shares' closing price on Wednesday.

"I don't think there's anything that's happened that's been totally surprising," Goss said.

Clear Channel also said it plans to sell 448 of its radio stations, all located outside the top 100 markets, as well as its 42-station television group, which are also located in smaller markets. Collectively the properties made up less than 10 percent of the company's revenues last year.

The acquisition is not dependent on the sale of those assets, the company said.

Clear Channel owns or operates 1,150 radio stations and is the largest operator of radio stations in the country.

Kit Spring, an analyst for Stifel Nicolaus & Co. Inc., wrote in a note that shareholders should reject the initial offer.

"(Clear Channel's) assets could command a much higher price if sold piece by piece, in our view," the note said.

Moran said the other "wild card" in Thursday's announcement was the fate of Clear Channel Outdoor, a major operator of billboard and bus-stop ads. Clear Channel owns a majority of the outdoor business, which trades separately.

Outdoor advertising company JCDecaux last week expressed interest in acquiring Clear Channel Outdoor.

Thursday's announcement doesn't include any provisions for taking the public portion of Clear Channel Outdoor private, the company said. However, Clear Channel's majority ownership of Clear Channel Outdoor will transfer to the private equity group.

The company's directors have approved the agreement, with the board insiders recused from the vote.

Once stock market darlings, radio stocks have fallen out of favor on Wall Street in recent years amid sluggish advertising revenues and competition from the boom in portable listening devices like Apple Computer Inc.'s iPods and the emerging growth of satellite radio.

Since January of 2000, Clear Channel stock has fallen from a high of more than $90.

Clear Channel has instituted several measures to try to win listeners back, including cutting back on the number of commercials. However other operators have yet to embrace its "less is more" strategy.

Clear Channel was founded in 1972 and benefited greatly from the loosening of media ownership rules, which allowed more radio stations to be held by a single owner in each market.

The deal would rank behind KKR's 1988 buyout of RJR Nabisco Inc., which still is the biggest going-private deal ever at $25.1 billion. It would also trail two other deals announced earlier this year. Those included the $21.8 billion buyout of airport development company BAA PLC and the $21.3 billion buyout of hospital company HCA Inc.

Clear Channel said it expects to close the acquisition by the fourth quarter of next year.

And beyond that?

"Maybe they won't be private forever," said Goss. "That's always a possibility (going public again) because private equity usually has an exit strategy. They don't really buy it just to own it forever. ... If it were public again it wouldn't look the same day as it did the first time around."