Covered Assets and FDIC Loss-sharing Asset (Changes in Accretable Yield for Acquired Loans) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Covered Assets And FDIC Loss Sharing Asset
Balance at beginning of period	$ 259,669	$ 256,572
Additions resulting from acquisitions	0	59,810
Accretion	(86,671)	(90,378)
Disposals	(12,856)	(31,483)
Reclassifications from nonaccretable difference	6,746	65,148
Balance at end of period	$ 166,888	$ 259,669