Acquisitions - Assets Acquired and Liabilities Assumed - Schedule (Details) - USD ($) $ in Thousands				2 Months Ended	3 Months Ended	9 Months Ended
	Jul. 01, 2018	Dec. 31, 2017	Apr. 01, 2017	Dec. 31, 2017	Sep. 30, 2018	Dec. 31, 2017	Nov. 01, 2017
LIABILITIES ASSUMED
Goodwill recognized		$ 493,329		$ 493,329	$ 807,892	$ 493,329
Grandpoint Capital, Inc.
ASSETS ACQUIRED
Cash and cash equivalents	$ 147,551				147,551
Investment securities	395,905				392,858
Loans, gross	2,404,042				2,352,388
Allowance for loan losses	(18,665)				0
Fixed assets	6,015				9,122
Core deposit intangible	5,093				71,943
Deferred tax assets	14,185				4,536
Other assets	97,441				97,246
Total assets acquired	3,051,567				3,075,644
LIABILITIES ASSUMED
Deposits	2,506,663				2,506,929
Borrowings	255,155				254,923
Other Liabilities	23,687				24,859
Total liabilities assumed	2,785,505				2,786,711
Excess of assets acquired over liabilities assumed	266,062				288,933
Consideration paid	629,000				601,172
Goodwill recognized	$ 312,000				312,239
Fair Value Adjustments
Cash and cash equivalents					0
Investment securities					(3,047)
Loans, gross					(51,654)
Allowance for loan losses					18,665
Fixed assets					3,107
Core deposit intangible					66,850
Deferred tax assets					(9,649)
Other assets					(195)
Total assets acquired					24,077
Deposits					266
Borrowings					(232)
Other Liabilities					1,172
Total liabilities assumed					1,206
Excess of assets acquired over liabilities assumed					$ 22,871
Plaza Bancorp
ASSETS ACQUIRED
Cash and cash equivalents		150,459		150,459		150,459	$ 150,459
Loans, gross		1,062,901		1,062,901		1,062,901	1,069,359
Allowance for loan losses		0		0		0	(13,009)
Fixed assets		7,195		7,195		7,195	7,389
Core deposit intangible		10,773		10,773		10,773	198
Deferred tax assets		5,506		5,506		5,506	11,849
Other assets		18,906		18,906		18,906	19,495
Total assets acquired		1,255,740		1,255,740		1,255,740	1,245,740
LIABILITIES ASSUMED
Deposits		1,082,951		1,082,951		1,082,951	1,081,727
Borrowings		41,152		41,152		41,152	40,755
Other Liabilities		8,505		8,505		8,505	8,956
Total liabilities assumed		1,132,608		1,132,608		1,132,608	1,131,438
Excess of assets acquired over liabilities assumed		123,132		123,132		123,132	$ 114,302
Consideration paid		246,000		245,761
Goodwill recognized		122,629		122,629		122,629
Fair Value Adjustments
Cash and cash equivalents				0
Loans, gross				(6,458)
Allowance for loan losses				13,009
Fixed assets				(194)
Core deposit intangible				10,575
Deferred tax assets				(6,343)
Other assets				(589)
Total assets acquired				10,000
Deposits				1,224
Borrowings				397
Other Liabilities				(451)
Total liabilities assumed				1,170
Excess of assets acquired over liabilities assumed				8,830
Heritage Oaks Bancorp
ASSETS ACQUIRED
Cash and cash equivalents		78,728	$ 78,728	78,728		78,728
Investment securities		442,923	445,299	442,923		442,923
Loans, gross		1,364,688	1,384,949	1,364,688		1,364,688
Allowance for loan losses		0	(17,200)	0		0
Fixed assets		34,902	35,567	34,902		34,902
Core deposit intangible		28,123	3,207	28,123		28,123
Deferred tax assets		10,244	17,850	10,244		10,244
Other assets		55,214	55,235	55,214		55,214
Total assets acquired		2,014,822	2,003,635	2,014,822		2,014,822
LIABILITIES ASSUMED
Deposits		1,669,550	1,668,085	1,669,550		1,669,550
Borrowings		139,034	139,150	139,034		139,034
Other Liabilities		8,352	8,059	8,352		8,352
Total liabilities assumed		1,816,936	1,815,294	1,816,936		1,816,936
Excess of assets acquired over liabilities assumed		197,886	188,341	197,886		197,886
Consideration paid			467,000			467,439
Goodwill recognized		$ 269,553	$ 270,000	$ 269,553		269,553
Fair Value Adjustments
Cash and cash equivalents						0
Investment securities						(2,376)
Loans, gross						(20,261)
Allowance for loan losses						17,200
Fixed assets						(665)
Core deposit intangible						24,916
Deferred tax assets						(7,606)
Other assets						(21)
Total assets acquired						11,187
Deposits						1,465
Borrowings						(116)
Other Liabilities						293
Total liabilities assumed						1,642
Excess of assets acquired over liabilities assumed						$ 9,545