Derivative Instruments - Summary of Notional for VIE Derivatives Outstanding (Detail) - Variable Interest Entity, Primary Beneficiary [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Interest Rate Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 1,399,532	$ 1,483,491
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	1,176,748	2,479,244
Currency Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	344,992	394,541
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	$ 10,254	$ 12,100