Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands				12 Months Ended
	Jul. 01, 2018	Nov. 01, 2017	Apr. 02, 2017	Jun. 30, 2019	Nov. 01, 2018	Mar. 31, 2018	Dec. 31, 2019	Jul. 01, 2019	Dec. 31, 2018	Apr. 01, 2018	Dec. 31, 2017	Apr. 01, 2017	Mar. 31, 2017	Dec. 31, 2016
LIABILITIES ASSUMED
Goodwill recognized							$ 808,322		$ 808,726		$ 493,329			$ 102,490
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							5,028
Other assets	97,441							97,005
Total assets acquired	3,051,567							3,076,224
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							289,513
Consideration paid	$ 602,200			$ 602,152
Goodwill recognized								$ 312,639
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				(9,157)
Other assets				(436)
Total assets acquired				24,657
Deposits				266
Borrowings				(232)
Other Liabilities				1,172
Total liabilities assumed				1,206
Excess of assets acquired over liabilities assumed				$ 23,451
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	$ 2,010,000
LIABILITIES ASSUMED
Deposits										1,669,550		1,668,085	$ 1,670,000
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