Covered Assets and FDIC Loss-sharing Asset (Changes in Accretable Yield for Acquired Loans) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended		15 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012
Covered Assets And FDIC Loss Sharing Asset
Balance at beginning of period	$ 214,061	$ 259,669	$ 256,572	$ 314,333
Accretion	(19,571)	(69,045)	(60,369)	(23,608)
Disposals	(3,146)	(8,218)	(24,134)	(8,594)
Reclassifications (to) from nonaccretable difference	(2,861)	6,077	50,320	69
Balance at end of period	$ 188,483	$ 188,483	$ 282,200	$ 188,483