COMMITMENTS AND CONTINGENCIES - Schedule of Guarantor Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments to extend credit	$ 3,550,269	$ 2,826,719
Unused home equity lines of credit	262,576	259,015
Financial standby letters of credit	32,291	33,613
Mortgage interest rate lock commitments	$ 674,525	$ 1,199,939