Though details of BB&T Corp.'s (BBT) expected deal for Colonial BancGroup Inc. (CNB) were unknown, investors on Friday embraced news of a transaction that would help BB&T get one step further in its aim toward become a leading bank.

Winston-Salem, N.C.-based BB&T has been an active acquirer for decades and, in recent years, said it explored potential mergers of equals. Nothing came of it.

Meanwhile, BB&T came through the financial crisis stronger than most regional banks, though bad loans are mounting.

A deal to acquire Colonial's branches and deposits would give BB&T a much-expanded branch network in Florida, a beachhead in Texas, likely considerable cost savings, and, at least initially, $20 billion more in deposits. That might well "help BB&T to the next level," said Thomas Michaud, the president of Keefe, Bruyette & Woods Inc.

"It's probably accretive right away" and "it'll give BB&T even more fire power" to help pull it through the crisis and expand further, Michaud said.

BB&T might get the Colonial assets "essentially for free," said Sandler O'Neill & Partners LP analyst Kevin Fitzsimmons, because it was expected that the Federal Deposit Insurance Corp. will take Colonial into receivership.

BB&T shares gained 9.4% to finish Friday's session at $28.23, its highest closing level since December.

But there are some risks: Colonial, with its $25 billion in assets, is a sizable purchase with all the integration risk that comes with folding an acquisition into existing operations. Fitzsimmons noted that BB&T hasn't done a big deal in a while.

An expansion in Florida is an attractive part of the deal for BB&T, but it remains unclear when Florida's economy and housing market will stabilize enough to provide attractive returns.

Questions also remained about what kind of assets BB&T is taking on, which parts of Colonial's souring loan book and legal risk BB&T would be able to leave behind, and what kind of guarantees the FDIC would provide.

"Given Colonial's risky loan portfolio, we would expect significant FDIC loss-sharing to be involved," FBR Capital Markets analyst Paul Miller said in a research report.

"We really need to know the details of the transaction and the extent of FDIC loss-sharing in order to determine how beneficial this transaction will be" for BB&T, he wrote. He added, though, that the transaction would be a "big positive" for BB&T if it involves just branches and deposits.

Unlike IndyMac Bancorp Inc. and some other struggling banks, Colonial has an attractive branch network and a good deposit base. Only about 10% of Colonial's deposits are brokered deposits, which are bundled deposits from investors rather than bank clients and which are typically more costly for the bank. Many of the banks that recently failed had a considerably higher share of such deposits, some more than half of overall deposits.

BB&T has an experienced management team in place that soothes the nerves of the FDIC, which has to protect the taxpayer. In handing Colonial to BB&T, the FDIC would be strengthening BB&T. And the cost savings would allow BB&T to achieve a higher return.

-By Matthias Rieker, Dow Jones Newswires; 212-416-2471; matthias.rieker@dowjones.com