Acquisitions - Assets Acquired and Liabilities Assumed - Schedule (Details) - USD ($) $ in Thousands			8 Months Ended	15 Months Ended
	Nov. 01, 2017	Apr. 01, 2017	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
LIABILITIES ASSUMED
Goodwill recognized			$ 494,672	$ 494,672	$ 493,329
Plaza Bancorp
ASSETS ACQUIRED
Cash and cash equivalents	$ 150,459		150,459	150,459
Loans, gross	1,069,359		1,062,901	1,062,901
Allowance for loan losses	(13,009)		0	0
Fixed assets	7,389		7,195	7,195
Core deposit intangible	198		10,773	10,773
Deferred tax assets	11,849		5,506	5,506
Other assets	19,495		18,906	18,906
Total assets acquired	1,245,740		1,255,740	1,255,740
LIABILITIES ASSUMED
Deposits	1,081,727		1,082,951	1,082,951
Borrowings	40,755		41,152	41,152
Other Liabilities	8,956		8,505	8,505
Total liabilities assumed	1,131,438		1,132,608	1,132,608
Excess of assets acquired over liabilities assumed	114,302		123,132	123,132
Consideration paid	246,000		245,761
Goodwill recognized	$ 123,000		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
Investment securities		445,299	442,923	442,923
Loans, gross		1,384,949	1,364,688	1,364,688
Allowance for loan losses		(17,200)	0	0
Fixed assets		35,567	34,902	34,902
Core deposit intangible		3,207	28,123	28,123
Deferred tax assets		17,850	10,244	10,244
Other assets		55,235	55,214	55,214
Total assets acquired		2,003,635	2,014,822	2,014,822
LIABILITIES ASSUMED
Deposits		1,668,085	1,669,550	1,669,550
Borrowings		139,150	139,034	139,034
Other Liabilities		8,059	8,352	8,352
Total liabilities assumed		1,815,294	1,816,936	1,816,936
Excess of assets acquired over liabilities assumed		188,341	197,886	197,886
Consideration paid		467,000		467,439
Goodwill recognized		$ 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