ACQUISITIONS - Acquisition of FCB Bancorp, Inc. (Details) $ / shares in Units, $ in Thousands		3 Months Ended
	Dec. 19, 2016 USD ($) $ / shares	Mar. 31, 2017 item	Apr. 28, 2017 $ / shares	Jan. 31, 2017 USD ($)
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			$ 34.20
Approximate value of transaction	$ 59,000
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]
Number of branches acquired | item		7
Assets of acquiree				$ 519,206
Loans receivable of acquiree				436,596
Deposits				383,402
Total equity of acquiree				$ 30,396