Selected Quarterly Financial Data Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest Income (Expense), Net [Abstract]
Interest Income	$ 243,497	$ 207,672	$ 218,455	$ 214,314	$ 209,696	$ 202,356	$ 204,363	$ 88,360	$ 883,938	$ 704,775	$ 309,914
Interest expense	(14,298)	(15,152)	(15,903)	(15,239)	(14,713)	(13,510)	(11,830)	(2,345)	(60,592)	(42,398)	(12,201)
Net interest income	229,199	192,520	202,552	199,075	194,983	188,846	192,533	86,015	823,346	662,377	297,713
Provision (negative provision) for credit losses	13,772	8,746	6,529	16,434	2,063	5,050	5,030	644	45,481	11,499	(4,210)
FDIC loss sharing expense, net	(4,291)	(4,449)	(5,107)	(4,399)	(4,360)	(7,415)	(8,525)	(11,430)	(18,246)	(31,730)	(26,172)
Noninterest Income [Abstract]
Gain on securities	0	655	(186)	3,275	0	0	89	4,752	3,744	4,841	5,359
Noninterest Income, Other	32,349	19,552	24,916	21,995	17,063	23,729	16,915	11,369
Total noninterest income	28,058	15,758	19,623	20,871	12,703	16,314	8,479	4,691	84,310	42,187	4,244
Foreclosed Assets (Income) Expense, Net	3,185	(4,521)	2,340	(336)	(1,938)	(4,827)	(497)	1,861	668	(5,401)	1,503
Noninterest Expense [Abstract]
Additions	(17,600)	(747)	(900)	(2,000)	(7,381)	(5,193)	(86,242)	(2,200)	(9,410)	(6,268)	(5,402)
Acquisition, integration and reorganization costs	(107,849)	(84,871)	(86,716)	(82,024)	(81,986)	(84,903)	(82,461)	(49,825)	(21,247)	(101,016)	(40,812)
Total noninterest expense	(122,264)	(90,139)	(85,276)	(84,360)	(91,305)	(94,923)	(169,200)	(50,164)	(382,039)	(405,592)	(228,165)
Income (Loss) from Continuing Operations Attributable to Parent [Abstract]
Earnings from continuing operations before taxes	121,221	109,393	130,370	119,152	114,318	105,187	26,782	41,186	480,136	287,473	78,002
Income Tax Expense (Benefit)	(49,380)	(39,777)	(45,287)	(46,073)	(43,261)	(42,911)	(15,552)	(15,281)	(180,517)	(117,005)	(32,525)
Net earnings from continuing operations					71,057	62,276	11,230	25,905	299,619	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)	0	(2,677)	(620)
Income tax benefit					47	3	476	588	0	1,114	258
Net loss from discontinued operations					(58)	(5)	(675)	(825)	0	(1,563)	(362)
Net earnings	$ 71,841	$ 69,616	$ 85,083	$ 73,079	$ 70,999	$ 62,271	$ 10,555	$ 25,080	$ 299,619	$ 168,905	$ 45,115
Earnings Per Share, Basic [Abstract]
Net earnings from continuing operations					$ 0.69	$ 0.60	$ 0.11	$ 0.57	$ 2.79	$ 1.94	$ 1.09
Basic net income per share (usd per share)	$ 0.60	$ 0.68	$ 0.83	$ 0.71	0.69	0.60	0.10	0.55	2.79	1.92	1.08
Earnings Per Share, Diluted [Abstract]
Net earnings from continuing operations					0.69	0.60	0.11	0.57	2.79	1.94	1.09
Diluted net income per share (usd per share)	$ 0.60	$ 0.68	$ 0.83	$ 0.71	$ 0.69	$ 0.60	$ 0.10	$ 0.55	$ 2.79	$ 1.92	$ 1.08