Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands					6 Months Ended	12 Months Ended
	Jul. 01, 2018	Nov. 01, 2017	Apr. 02, 2017	Jan. 31, 2016	Dec. 31, 2018	Nov. 01, 2018	Mar. 31, 2018	Jan. 31, 2017	Apr. 01, 2018	Dec. 31, 2017	Apr. 01, 2017	Dec. 31, 2016	Dec. 31, 2015
LIABILITIES ASSUMED
Goodwill recognized					$ 808,726					$ 493,329		$ 102,490	$ 50,832
Grandpoint Capital, Inc.
ASSETS ACQUIRED
Cash and cash equivalents	$ 147,551				147,551
Investment securities	395,905				392,858
Loans, gross	2,404,042				2,352,717
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				4,383
Other assets	97,441				97,246
Total assets acquired	3,051,567				3,075,820
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				289,109
Consideration paid	$ 601,200				602,152
Goodwill recognized					313,043
Fair Value Adjustment
Cash and cash equivalents					0
Investment securities					(3,047)
Loans, gross					(51,325)
Allowance for loan losses					18,665
Fixed assets					3,107
Core deposit intangible					66,850
Deferred tax assets					(9,802)
Other assets					(195)
Total assets acquired					24,253
Deposits					266
Borrowings					(232)
Other Liabilities					1,172
Total liabilities assumed					1,206
Excess of assets acquired over liabilities assumed					23,047
Plaza Bancorp
ASSETS ACQUIRED
Cash and cash equivalents		$ 150,459				$ 150,459
Loans, gross		1,069,359				1,062,901
Allowance for loan losses		(13,009)				0
Fixed assets		7,389				5,965
Core deposit intangible		198				10,773
Deferred tax assets		11,849				5,726
Other assets		19,495				18,906
Total assets acquired		1,245,740				1,254,730
LIABILITIES ASSUMED
Deposits		1,081,727				1,082,951
Borrowings		40,755				41,152
Other Liabilities		8,956				8,506
Total liabilities assumed		1,131,438				1,132,609
Excess of assets acquired over liabilities assumed		114,302				122,121
Consideration paid		245,800				245,761
Goodwill recognized		$ 124,000				123,640
Fair Value Adjustment
Cash and cash equivalents						0
Loans, gross						(6,458)
Allowance for loan losses						13,009
Fixed assets						(1,424)
Core deposit intangible						10,575
Deferred tax assets						(6,123)
Other assets						(589)
Total assets acquired						8,990
Deposits						1,224
Borrowings						397
Other Liabilities						(450)
Total liabilities assumed						1,171
Excess of assets acquired over liabilities assumed						$ 7,819
Heritage Oaks Bank
ASSETS ACQUIRED
Cash and cash equivalents									$ 78,728		$ 78,728
Investment securities									442,923		445,299
Loans, gross									1,364,688		1,384,949
Allowance for loan losses									0		(17,200)
Fixed assets									34,902		35,567
Core deposit intangible									28,123		3,207
Deferred tax assets									10,244		17,850
Other assets									55,214		55,235
Total assets acquired									2,014,822		2,003,635
LIABILITIES ASSUMED
Deposits									1,669,550		1,668,085
Borrowings									139,034		139,150
Other Liabilities									8,352		8,059
Total liabilities assumed									1,816,936		1,815,294
Excess of assets acquired over liabilities assumed									197,886		188,341
Consideration paid			$ 467,400				$ 467,439
Goodwill recognized									$ 269,553		$ 270,000
Fair Value Adjustment
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
Security California Bancorp
ASSETS ACQUIRED
Cash and cash equivalents				$ 40,947				$ 40,947
Investment securities				191,881				190,254
Loans, gross				467,197				456,158
Allowance for loan losses				(7,399)				0
Fixed assets				5,335				4,190
Core deposit intangible				493				4,319
Deferred tax assets				5,618				6,748
Other assets				10,589				9,362
Total assets acquired				716,633				713,950
LIABILITIES ASSUMED
Deposits				636,450	$ 636,600			636,591
Borrowings				0				0
Deferred tax liability				0				0
Other Liabilities				9,063				8,843
Total liabilities assumed				645,513				645,434
Excess of assets acquired over liabilities assumed				71,120				68,516
Consideration paid				120,200				120,174
Goodwill recognized				51,700				51,658
Fair Value Adjustment
Cash and cash equivalents								0
Investment securities								(1,627)
Loans, gross								(11,039)
Allowance for loan losses								7,399
Fixed assets								(1,145)
Core deposit intangible								3,826
Deferred tax assets								1,130
Other assets								(1,227)
Total assets acquired								(2,683)
Deposits								141
Borrowings								0
Deferred tax liability								0
Other Liabilities								(220)
Total liabilities assumed								(79)
Excess of assets acquired over liabilities assumed								(2,604)
Security California Bancorp | Bank Time Deposits
ASSETS ACQUIRED
Cash and cash equivalents				$ 1,972				1,972
Fair Value Adjustment
Cash and cash equivalents								$ 0