COMMITMENTS AND CONTINGENCIES - Schedule of Guarantor Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments to extend credit	$ 1,102,240	$ 1,109,806
Unused home equity lines of credit	71,138	69,788
Financial standby letters of credit	11,960	11,389
Mortgage interest rate lock commitments	153,809	86,149
Mortgage forward contracts with positive fair value	$ 97,032	$ 31,500