Derivative Instruments - Summary of Notional for VIE Derivatives Outstanding (Detail) - Variable Interest Entity, Primary Beneficiary [Member] - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Interest Rate Swap [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 1,103,656	$ 1,399,532
Interest Rate Swaps-Pay-Fixed/Receive-Variable [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	1,103,199	1,176,748
Currency Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	312,264	344,992
Other Credit Derivatives [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 8,676	$ 10,254