Quarterly Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 118,538	$ 115,960	$ 104,015	$ 104,333	$ 112,741	$ 114,108	$ 113,594	$ 115,642	$ 442,846		$ 456,085		$ 501,753
Interest expense	8,464	9,151	10,122	10,144	10,912	12,068	12,582	13,287	37,881		48,849		73,301
Net interest income	110,074	106,809	93,893	94,189	101,829	102,040	101,012	102,355	404,965		407,236		428,452
Provision for non-covered loan and lease losses	3,840	3,008	2,993	6,988	4,913	7,078	6,638	3,167	16,829		21,796		46,220
(Recapture of) provision for covered loan losses	(1,369)	(1,904)	(3,072)	232	3,103	2,927	1,406	(31)	(6,113)		7,405		16,141
Non-interest income	26,785	26,144	34,497	34,015	46,987	33,679	28,926	27,237	121,441		136,829		84,118
Non-interest expense	95,364	95,604	87,931	85,762	98,046	86,974	86,936	87,696	364,661		359,652		338,971
Income before provision for income taxes	39,024	36,245	40,538	35,222	42,754	38,740	34,958	38,760	151,029		155,212		111,238
Provision for income taxes	13,754	12,768	14,285	11,861	14,796	13,587	11,681	13,257	52,668		53,321		36,742
Net income	25,270	23,477	26,253	23,361	27,958	25,153	23,277	25,503	98,361		101,891		74,496
Dividends and undistributed earnings allocated to participating securities	212	196	197	183	183	170	162	167	788	[1]	682	[1]	356	[1]
Net earnings available to common shareholders	$ 25,058	$ 23,281	$ 26,056	$ 23,178	$ 27,775	$ 24,983	$ 23,115	$ 25,336	$ 97,573		$ 101,209		$ 74,140
Basic earnings per common share	$ 0.22	$ 0.21	$ 0.23	$ 0.21	$ 0.25	$ 0.22	$ 0.21	$ 0.23	$ 0.87		$ 0.90		$ 0.65
Diluted earnings per common share	$ 0.22	$ 0.21	$ 0.23	$ 0.21	$ 0.25	$ 0.22	$ 0.21	$ 0.23	$ 0.87		$ 0.90		$ 0.65
Cash dividends declared per common share	$ 0.15	$ 0.15	$ 0.20	$ 0.10	$ 0.09	$ 0.09	$ 0.09	$ 0.07

[1] Represents dividends paid and undistributed earnings allocated to nonvested restricted stock awards.