Acquisitions - Assets Acquired and Liabilities Assumed - Schedule (Details) - USD ($) $ in Thousands			6 Months Ended	9 Months Ended	20 Months Ended
	Apr. 01, 2017	Jan. 31, 2016	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill			$ 371,677	$ 371,677	$ 371,677	$ 102,490
Heritage Oaks Bancorp
Business Acquisition [Line Items]
Cash and cash equivalents	$ 78,728		78,728	78,728	78,728
Investment securities	447,520		442,923	442,923	442,923
FHLB stock	9,739		9,739	9,739	9,739
Loans, gross	1,387,949		1,364,649	1,364,649	1,364,649
Allowance for loan losses	(17,200)		0	0	0
Fixed assets	35,567		34,902	34,902	34,902
Core deposit intangible	0		28,123	28,123	28,123
Deferred income taxes	17,850		9,986	9,986	9,986
Other assets	45,484		45,475	45,475	45,475
Total assets acquired	2,005,637		2,014,525	2,014,525	2,014,525
Deposits	1,668,079		1,669,550	1,669,550	1,669,550
Borrowings	141,996		139,034	139,034	139,034
Other Liabilities	7,290		8,061	8,061	8,061
Total liabilities assumed	1,817,365		1,816,645	1,816,645	1,816,645
Excess of assets acquired over liabilities assumed	188,272		197,880	197,880	197,880
Consideration paid	465,000			465,482
Capitalized merger-related expense			1,585	1,585	1,585
Goodwill	$ 269,000		269,187	269,187	269,187
Fair Value Adjustments
Cash and cash equivalents			0
Investment securities			(4,597)
FHLB stock			0
Loans, gross			(23,300)
Allowance for loan losses			17,200
Fixed assets			(665)
Core deposit intangible			28,123
Deferred tax assets			(7,864)
Other assets			(9)
Total assets acquired			8,888
Deposits			1,471
Borrowings			(2,962)
Other Liabilities			771
Total liabilities assumed			(720)
Excess of assets acquired over liabilities assumed			9,608
Security California Bancorp
Business Acquisition [Line Items]
Cash and cash equivalents		$ 40,947	40,947	40,947	40,947
Interest-bearing deposits with financial institutions		1,972	1,972	1,972	1,972
Investment securities		191,881	190,254	190,254	190,254
Loans, gross		467,197	456,158	456,158	456,158
Allowance for loan losses		(7,399)	0	0	0
Fixed assets		5,335	4,190	4,190	4,190
Core deposit intangible		493	4,319	4,319	4,319
Deferred income taxes		5,618	6,748	6,748	6,748
Other assets		10,589	9,362	9,362	9,362
Total assets acquired		716,633	713,950	713,950	713,950
Deposits		636,450	636,591	636,591	636,591
Other Liabilities		9,063	8,843	8,843	8,843
Total liabilities assumed		645,513	645,434	645,434	645,434
Excess of assets acquired over liabilities assumed		71,120	68,516	68,516	68,516
Consideration paid		120,000		120,174
Goodwill		$ 51,700	$ 51,658	$ 51,658	51,658
Fair Value Adjustments
Cash and cash equivalents					0
Interest-bearing deposits with financial institutions					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
Other Liabilities					(220)
Total liabilities assumed					(79)
Excess of assets acquired over liabilities assumed					$ (2,604)