Quarterly Financial Information (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Quarterly Financial Information [Abstract]
Interest income	$ 112,741,000	$ 114,108,000	$ 113,594,000	$ 115,642,000	$ 121,917,000	$ 126,527,000	$ 128,417,000	$ 124,892,000	$ 456,085,000		$ 501,753,000		$ 488,596,000
Interest expense	10,912,000	12,068,000	12,582,000	13,287,000	15,262,000	18,993,000	19,056,000	19,990,000	48,849,000		73,301,000		93,812,000
Net interest income	101,829,000	102,040,000	101,012,000	102,355,000	106,655,000	107,534,000	109,361,000	104,902,000	407,236,000		428,452,000		394,784,000
Provision for non-covered loan and lease losses	4,913,000	7,078,000	6,638,000	3,167,000	6,642,000	9,089,000	15,459,000	15,030,000	21,796,000		46,220,000		113,668,000
Provision for covered loan and lease losses	3,103,000	2,927,000	1,406,000	(31,000)	698,000	4,420,000	3,755,000	7,268,000	7,405,000		16,141,000		5,151,000
Non-interest income	46,987,000	33,679,000	28,926,000	27,237,000	18,128,000	24,778,000	19,627,000	21,585,000	136,829,000		84,118,000		75,904,000
Non-interest expense	98,046,000	86,974,000	86,936,000	87,696,000	85,339,000	86,224,000	83,207,000	84,201,000	359,652,000		338,971,000		317,738,000
Income before provision for income taxes	42,754,000	38,740,000	34,958,000	38,760,000	32,104,000	32,579,000	26,567,000	19,988,000	155,212,000		111,238,000		34,131,000
Provision for income taxes	14,796,000	13,587,000	11,681,000	13,257,000	10,722,000	10,717,000	8,782,000	6,521,000	53,321,000		36,742,000		5,805,000
Net income	27,958,000	25,153,000	23,277,000	25,503,000	21,382,000	21,862,000	17,785,000	13,467,000	101,891,000		74,496,000		28,326,000
Preferred stock dividends													3,686,000
Dividends and undistributed earnings allocated to participating securities	183,000	170,000	162,000	167,000	103,000	105,000	86,000	62,000	682,000	[1]	356,000	[1]	67,000	[1]
Net earnings available to common shareholders	27,775,000	24,983,000	23,115,000	25,336,000	21,279,000	21,757,000	17,699,000	13,405,000	101,209,000		74,140,000		16,067,000
Basic earnings (loss) per common share	$ 0.25	$ 0.22	$ 0.21	$ 0.23	$ 0.19	$ 0.19	$ 0.15	$ 0.12	$ 0.90		$ 0.65		$ 0.15
Diluted	$ 0.25	$ 0.22	$ 0.21	$ 0.23	$ 0.19	$ 0.19	$ 0.15	$ 0.12	$ 0.90		$ 0.65		$ 0.15
Cash dividends declared per common share	$ 0.09	$ 0.09	$ 0.09	$ 0.07	$ 0.07	$ 0.07	$ 0.05	$ 0.05	$ 38,324,000		$ 27,471,000		$ 22,032,000

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