LOANS HELD FOR INVESTMENT - Loan Portfolio Held for Investment (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loans held for investment	$ 11,777,289	$ 9,002,205
Allowance for credit losses on loans and finance leases	385,887	155,139	$ 196,362	$ 231,843
Loans, net of allowance for credit losses	11,391,402	8,847,066
Residential Portfolio Segment [Member]
Loans held for investment	3,521,954	2,933,773
Allowance for credit losses on loans and finance leases	120,311	44,806	50,794	58,975
Commercial Portfolio Segment [Member] | Commercial and Industrial loans [Member]
Loans held for investment	3,202,590	2,230,876
Allowance for credit losses on loans and finance leases	37,944	15,198	32,546	48,871
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Loans held for investment	2,230,602	1,444,586
Allowance for credit losses on loans and finance leases	109,342	39,194	55,581	48,493
Commercial Portfolio Segment [Member] | Construction loans [Member]
Loans held for investment	212,500	111,317
Allowance for credit losses on loans and finance leases	5,380	2,370	3,592	4,522
Consumer Portfolio Segment [Member]
Loans held for investment	2,609,643	2,281,653
Allowance for credit losses on loans and finance leases	$ 112,910	$ 53,571	$ 53,849	$ 70,982