Business Segment (Details 2) (USD $) In Thousands, 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
Segment Reporting Information [Line Items]
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)
Intersegment interest income (expense), net									0	0	0
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 for credit losses	(2,063)	(5,050)	(5,030)	644	1,338	4,167	1,842	(3,137)	(11,499)	4,210	12,819
Gain on securities	0	0	89	4,752	(272)	5,222	0	409	4,841	5,359	1,239
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)
Other noninterest income	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
Foreclosed assets (expense) income, net	(1,938)	(4,827)	(497)	1,861	569	420	14	500	(5,401)	1,503	(10,931)
Intangible asset amortization	(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)
Debt Termination Expenses											(22,598)
Other noninterest expense					(66,088)	(56,200)	(64,216)	(44,183)	(296,059)	(185,976)	(167,718)
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									170,468	45,477	56,801
Intersegment noninterest income (expense_									0
Total noninterest expense - adjusted									(408,744)
Earnings (loss) 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
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
Operating Segments [Member] | Pacific Western Bank [Member]
Segment Reporting Information [Line Items]
Interest Income									279,671	261,492	251,720
Interest expense									(27,598)	(7,873)	(15,043)
Intersegment interest income (expense), net									15,716	1,525	2,055
Net interest income									267,789	255,144	238,732
Provision for credit losses									21,311	8,079	14,585
Gain on securities									4,841	137	1,239
FDIC loss sharing expense, net									(31,730)	(26,172)	(10,070)
Other noninterest income									25,168	21,395	20,572
Total non-interest income									(1,721)	(4,640)	11,741
Foreclosed assets (expense) income, net									(5,685)	1,503	(10,931)
Intangible asset amortization									(5,745)	(4,748)	(5,898)
Acquisition, integration and reorganization costs									(89,888)	(40,552)	(4,089)
Debt Termination Expenses											(24,195)
Other noninterest expense									(198,921)	(156,600)	(138,640)
Total noninterest expense									(300,239)	(200,397)	(183,753)
Intersegment noninterest income (expense_									71,897
Total noninterest expense - adjusted									(228,342)
Earnings (loss) from continuing operations before taxes									59,037	58,186	81,305
Income Tax Expense (Benefit)									(27,370)	(24,940)	(31,542)
Net earnings from continuing operations									31,667	33,246
Loss from discontinued operations before taxes									(2,677)	(620)
Income tax benefit									1,114	258
Net loss from discontinued operations									(1,563)	(362)
Net earnings									30,104	32,884	49,763
Operating Segments [Member] | National Lending Segment [Member]
Segment Reporting Information [Line Items]
Interest Income									422,677	48,422	44,395
Interest expense									(230)	(532)	(884)
Intersegment interest income (expense), net									(15,716)	(1,525)	(2,055)
Net interest income									406,731	46,365	41,456
Provision for credit losses									(32,810)	(3,869)	(1,766)
Gain on securities									0	0	0
FDIC loss sharing expense, net									0	0	0
Other noninterest income									34,215	3,558	4,017
Total non-interest income									34,215	3,558	4,017
Foreclosed assets (expense) income, net									(302)	0	0
Intangible asset amortization									(523)	(654)	(428)
Acquisition, integration and reorganization costs									(10,073)	0	0
Other noninterest expense									(80,418)	(23,575)	(23,502)
Total noninterest expense									(91,316)	(24,229)	(23,930)
Intersegment noninterest income (expense_									(71,897)
Total noninterest expense - adjusted									(163,213)
Earnings (loss) from continuing operations before taxes									244,923	21,825	19,777
Income Tax Expense (Benefit)									(97,853)	(9,101)	(8,327)
Net earnings from continuing operations									147,070	12,724
Loss from discontinued operations before taxes									0	0
Income tax benefit									0	0
Net loss from discontinued operations									0	0
Net earnings									147,070	12,724	11,450
Operating Segments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Interest Income									2,427	0	0
Interest expense									(14,570)	(3,796)	(3,721)
Intersegment interest income (expense), net									0	0	0
Net interest income									(12,143)	(3,796)	(3,721)
Provision for credit losses									0	0	0
Gain on securities									0	5,222	0
FDIC loss sharing expense, net									0	0	0
Other noninterest income									9,693	104	114
Total non-interest income									9,693	5,326	114
Foreclosed assets (expense) income, net									586	0	0
Intangible asset amortization									0	0	0
Acquisition, integration and reorganization costs									(1,055)	(260)	0
Debt Termination Expenses											1,597
Other noninterest expense									(16,720)	(5,801)	(5,576)
Total noninterest expense									(17,189)	(6,061)	(3,979)
Intersegment noninterest income (expense_									0
Total noninterest expense - adjusted									(17,189)
Earnings (loss) from continuing operations before taxes									(19,639)	(4,531)	(7,586)
Income Tax Expense (Benefit)									11,370	4,038	3,174
Net earnings from continuing operations									(8,269)	(493)
Loss from discontinued operations before taxes									0	0
Income tax benefit									0	0
Net loss from discontinued operations									0	0
Net earnings									$ (8,269)	$ (493)	$ (4,412)