Acquisitions - Narrative (Details) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
	Apr. 01, 2017 USD ($) shares	Jan. 31, 2016 USD ($) bank shares	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Mar. 31, 2017 $ / shares	Dec. 31, 2016 USD ($)	Jan. 29, 2016 USD ($) $ / shares
Business Acquisition [Line Items]
Assets			$ 6,532,334		$ 6,532,334		$ 4,036,311
Gross loans			5,054,231		5,054,231		3,245,694
Deposits			5,018,153		5,018,153		3,145,581
Closing stock price of common stock ($ per share) | $ / shares						$ 38.55		$ 20.53
Goodwill			371,677		371,677		$ 102,490
Adjustment to deferred tax assets and the deal consideration			1,100
Adjustment to fixed assets and goodwill				$ 146
Heritage Oaks Bancorp
Business Acquisition [Line Items]
Assets	$ 2,000,000
Gross loans	1,400,000
Deposits	$ 1,700,000
Equity issued (shares)	0.3471
Consideration paid	$ 465,000				465,482
Cash consideration	3,900
Goodwill	$ 269,000		269,187		269,187
Heritage Oaks Bancorp | Common Stock
Business Acquisition [Line Items]
Number of shares of common stock issued as consideration | shares	11,959,022
Security California Bancorp
Business Acquisition [Line Items]
Assets		$ 714,000
Gross loans		456,000
Deposits		$ 637,000
Equity issued (shares)		0.9629
Consideration paid		$ 120,000			120,174
Cash consideration		788
Goodwill		$ 51,700	$ 51,658		$ 51,658
Number of branches | bank		6
Security California Bancorp | Common Stock
Business Acquisition [Line Items]
Number of shares of common stock issued as consideration | shares		5,815,051
Value of shares of common stock issued as consideration								$ 119,000