Acquisitions - Security California Bancorp - Narrative (Details) $ / shares in Units, $ in Thousands		3 Months Ended
	Jan. 31, 2016 USD ($) bank shares	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 $ / shares	Dec. 31, 2016 USD ($)	Jan. 29, 2016 USD ($) $ / shares
Business Acquisition [Line Items]
Assets			$ 6,440,631		$ 4,036,311
Deposits			4,946,431		3,145,581
Closing stock price of common stock ($ per share) | $ / shares				$ 38.55		$ 20.53
Goodwill			$ 370,564		$ 102,490
Adjustment		$ 146
Security California Bancorp
Business Acquisition [Line Items]
Assets	$ 714,000
Total gross loans	456,000
Deposits	$ 637,000
Equity issued (shares)	0.9629
Consideration paid	$ 120,174
Cash consideration	$ 788
Number Of branches | bank	6
Goodwill	$ 51,658
Security California Bancorp | Common Stock
Business Acquisition [Line Items]
Number of shares of common stock issued as consideration | shares	5,815,051
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned						$ 119,000