ACQUISITIONS - Acquisition of FCB Bancorp, Inc. (Details) $ / shares in Units, $ in Thousands	Dec. 19, 2016 USD ($) $ / shares	Dec. 31, 2016 USD ($)	Dec. 16, 2016 $ / shares
FCB Bancorp, Inc.
Business Acquisition [Line Items]
Ratio of shares to be received by acquiree shareholders	0.9
Cash received in exchange for each share of common stock owned (in dollars per share) | $ / shares	$ 7.00
Closing price per share of common stock | $ / shares			$ 32.65
Approximate value of transaction	$ 56,900
FCB Bancorp, Inc. | Outstanding and Unexercised Options
Business Acquisition [Line Items]
Ratio of shares to be received by acquiree shareholders	0.9
Cash received in exchange for each share of common stock owned (in dollars per share) | $ / shares	$ 7.00
Period of consecutive trading days used to calculate average daily closing sales price of a share of common stock	10 days
FCB Bank
Business Acquisition [Line Items]
Assets of acquiree		$ 518,380
Loans receivable of acquiree		427,047
Deposits		387,862
Total equity of acquiree		$ 30,798