Acquisitions (Activity for Acquired Loans) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Activity for accretable yield includes contractually due interest of acquired loans
Balance at beginning of period	$ 49,390		$ 68,305
Additions (reductions)	(491)	[1]	4,006	[1]
Accretion recognized in interest income	(4,940)		(6,638)
Reclassification from nonaccretable difference	125		0
Balance at end of period	$ 44,084		$ 65,673

[1] Represents additions of estimated contractual interest expected to be collected from acquired loans being renewed or extended, less reductions in contractual interest resulting from the early payoff of acquired loans.