LOANS HELD FOR INVESTMENT - Corporation's TDR Activity (Parenthetical) (Detail) - TDR - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Troubled Debt Restructurings Paid Or Partial Paid	$ 37,992	$ 136,709	$ 99,373
Charge-offs post modification	(11,122)	$ (10,342)	$ (27,951)
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Troubled Debt Restructurings Paid Or Partial Paid	$ 92,400