COMMITMENTS AND CONTINGENT LIABILITIES - Schedule of Guarantor Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments to extend credit	$ 2,826,719	$ 2,486,949
Unused home equity lines of credit	259,015	262,089
Financial standby letters of credit	33,613	29,232
Mortgage interest rate lock commitments	$ 1,199,939	$ 288,490