Selected Quarterly Financial Data Selected Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest Income (Expense), Net [Abstract]
Interest Income	$ 209,696	$ 202,356	$ 204,363	$ 88,360					$ 704,775	$ 309,914	$ 296,115
Interest expense	(14,713)	(13,510)	(11,830)	(2,345)	(2,598)	(2,869)	(3,158)	(3,576)	(42,398)	(12,201)	(19,648)
Net interest income	194,983	188,846	192,533	86,015	81,258	82,289	68,473	65,693	662,377	297,713	276,467
Provision (negative provision) for credit losses	(2,063)	(5,050)	(5,030)	644	1,338	4,167	1,842	(3,137)	(11,499)	4,210	12,819
FDIC loss sharing expense, net	(4,360)	(7,415)	(8,525)	(11,430)	(10,593)	(7,032)	(5,410)	(3,137)	(31,730)	(26,172)	(10,070)
Noninterest Income [Abstract]
Gain on securities	0	0	89	4,752	(272)	5,222	0	409	4,841	5,359	1,239
Noninterest Income, Other	17,063	23,729	16,915	11,369	6,939	6,937	5,613	5,568	69,076	25,057	24,703
Total non-interest income	12,703	16,314	8,479	4,691	(3,926)	5,127	203	2,840	42,187	4,244	15,872
Noninterest Expense [Abstract]
Foreclosed assets (expense) income, net	(1,938)	(4,827)	(497)	1,861	569	420	14	500	(5,401)	1,503	(10,931)
Additions	(7,381)	(5,193)	(86,242)	(2,200)	(16,673)	(5,450)	(17,997)	(692)	(6,268)	(5,402)	(6,326)
Acquisition, integration and reorganization costs	(83,021)	(85,609)	(83,167)	(50,530)	(49,984)	(51,170)	(46,233)	(43,991)	(101,016)	(40,812)	(4,089)
Total noninterest expense	(92,340)	(95,629)	(169,906)	(50,869)					(408,744)	(230,687)	(211,662)
Income (Loss) from Continuing Operations Attributable to Parent [Abstract]
Earnings from continuing operations before taxes	113,283	104,481	26,076	40,481	12,582	35,383	6,302	21,213	284,321	75,480	93,496
Income Tax Expense (Benefit)	(42,226)	(42,205)	(14,846)	(14,576)	(9,135)	(11,243)	(1,906)	(7,719)	(113,853)	(30,003)	(36,695)
Net earnings from continuing operations	71,057	62,276	11,230	25,905	3,447	24,140	4,396	13,494	170,468	45,477
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent [Abstract]
Loss from discontinued operations before taxes	(105)	(8)	(1,151)	(1,413)	(578)	39	(81)	0	(2,677)	(620)	0
Income tax benefit	47	3	476	588	240	(16)	34	0	1,114	258	0
Net loss from discontinued operations	(58)	(5)	(675)	(825)	(338)	23	(47)	0	(1,563)	(362)	0
Net earnings	$ 70,999	$ 62,271	$ 10,555	$ 25,080	$ 3,109	$ 24,163	$ 4,349	$ 13,494	$ 168,905	$ 45,115	$ 56,801
Earnings Per Share, Basic [Abstract]
Net earnings from continuing operations	$ 690.00	$ 600.00	$ 110.00	$ 570.00	$ 70	$ 530.00	$ 110.00	$ 370.00	$ 1.94	$ 1.09	$ 1.54
Basic net income per share (usd per share)	$ 690.00	$ 600.00	$ 100.00	$ 550.00	$ 60	$ 530.00	$ 110.00	$ 370.00	$ 1.92	$ 1.08	$ 1.54
Earnings Per Share, Diluted [Abstract]
Net earnings from continuing operations	$ 690.00	$ 600.00	$ 110.00	$ 570.00	$ 70	$ 530.00	$ 110.00	$ 370.00	$ 1.94	$ 1.09	$ 1.54
Diluted net income per share (usd per share)	$ 690.00	$ 600.00	$ 100.00	$ 550.00	$ 60	$ 530.00	$ 110.00	$ 370.00	$ 1.92	$ 1.08	$ 1.54