COMMITMENTS AND CONTINGENCIES - Schedule of Guarantor Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments to extend credit	$ 1,722,454	$ 1,671,419
Unused home equity lines of credit	108,910	112,310
Financial standby letters of credit	25,419	24,596
Mortgage interest rate lock commitments	$ 204,087	$ 81,833