BUSINESS COMBINATION (Details) $ in Thousands		12 Months Ended
	Jan. 17, 2014 USD ($) entity banking_branch shares	Dec. 31, 2014 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2013 USD ($)
Business combination
Issuance of common stock pursuant to MetroCorp Bancshares, Inc. (“MetroCorp”) acquisition		$ 190,830
Goodwill recorded as a result of the business combination		469,433	$ 469,433	$ 337,438
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 the acquisition (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 given to acquiree's stock option holders as part of consideration transferred	2,400
Amount given for warrant's assumed as part of consideration transferred	8,800
Fair value of assets acquired	1,700,000
Fair value of liabilities acquired	1,410,000
Goodwill recorded as a result of the business combination	$ 121,000	132,000
MetroCorp | Adjustments
Business combination
Deferred tax assets		10,300
Bank owned life insurance		$ 700