San Antonio ? Three weeks.

That’s how long it took radio giant Clear Channel Communications Inc. 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 $8 billion in debt.

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

Clear Channel owns or operates 1,150 radio stations.