Covered Assets and FDIC Loss-sharing Asset (Changes in Accretable Yield for Acquired Loans) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Covered Assets And FDIC Loss Sharing Asset
Balance at beginning of period	$ 166,888	$ 259,669
Accretion	(14,477)	(27,658)
Disposals	(774)	(1,799)
Reclassifications (to) from nonaccretable difference	7,149	9,465
Balance at end of period	$ 158,786	$ 239,677