Loans, Leases and Allowance for Credit Losses - Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Financing Receivable, Not Past Due	$ 24,967,011	$ 21,065,187
Financing Receivable, Individually Evaluated for Impairment	$ 315,521	116,303
Non-accrual loans [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Not Past Due		$ 34,141