BUSINESS COMBINATION (Details) $ in Thousands		12 Months Ended
	Jan. 17, 2014 USD ($) entity banking_branch shares	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business combination
Issuance of common stock pursuant to MetroCorp Bancshares, Inc. (“MetroCorp”) acquisition		$ 190,830
Goodwill		469,433	$ 469,433	$ 469,433
MetroCorp
Business combination
Number of branches | banking_branch	19
Number of subsidiaries | entity	2
Percentage of purchase consideration satisfied in stock	66.67%
Percentage of purchase consideration satisfied in cash	33.33%
Fair value of the consideration transferred	$ 291,400
Consideration transferred (in shares) | shares	5,583,093
Issuance of common stock pursuant to MetroCorp Bancshares, Inc. (“MetroCorp”) acquisition	$ 190,800
Consideration transferred in cash	89,400
Additional cash to MetroCorp stock option holders	2,400
The fair value of a MetroCorp warrant	8,800
Fair value of assets acquired	1,700,000
Fair value of liabilities acquired	1,410,000
Goodwill	$ 121,000	132,000
MetroCorp | Adjustments
Business combination
Additional tax		(10,300)
Bank owned life insurance adjustment		$ (700)