COMMITMENTS AND CONTINGENCIES - Schedule of Guarantor Obligations (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments to extend credit	$ 1,096,702	$ 1,101,257
Unused home equity lines of credit	63,951	62,586
Financial standby letters of credit	13,192	14,257
Mortgage interest rate lock commitments	113,056	91,426
Mortgage forward contracts with positive fair value	$ 0	$ 150,000