COMMITMENTS AND CONTINGENCIES - Schedule of Guarantor Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments to extend credit	$ 1,818,407	$ 1,671,419
Unused home equity lines of credit	105,780	112,310
Financial standby letters of credit	25,599	24,596
Mortgage interest rate lock commitments	$ 158,141	$ 81,833