LOANS HELD FOR INVESTMENT - Loan Portfolio Held for Investment (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, before Allowance for Credit Loss	$ 11,060,658	$ 11,777,289
Unaccreted fair value net purchase discounts	35,300	48,000
Commercial Portfolio Segment [Member] \| COVID-19 [Member] \| US Government Insured Loan Program [Member]
Financing Receivable, before Allowance for Credit Loss	145,000	406,000
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member]
Financing Receivable, before Allowance for Credit Loss	2,887,251	3,202,590
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member] \| COVID-19 [Member] \| US Government Insured Loan Program [Member]
Financing Receivable, before Allowance for Credit Loss	145,000	406,000
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member] \| Commercial loans secured by real estate [Member]
Financing Receivable, before Allowance for Credit Loss	$ 1,000	$ 1,000

Amount, before allowance for credit loss, of financing receivable.

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