COMMITMENTS AND CONTINGENCIES - Schedule of Guarantor Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments to extend credit	$ 2,468,695	$ 2,486,949
Unused home equity lines of credit	261,647	262,089
Financial standby letters of credit	32,877	29,232
Mortgage interest rate lock commitments	$ 1,279,952	$ 288,490