ALLOWANCE FOR CREDIT LOSSES ON LOANS AND FINANCE LOSSES - Carrying Amount of Portfolios (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 11,847,275	$ 9,002,205
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,226,843	$ 2,230,876
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member] | COVID-19 | Small Business Administration
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 453,400