Derivative Instruments - Summary of Notional Amounts of AFS's Trading Derivative Products (Detail) - Successor [Member] - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 455,792	$ 737,380
AFS [Member] | 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	579,648	973,130
AFS [Member] | 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	281,920	1,874,678
AFS [Member] | Futures Contracts [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 1,105,000	$ 195,000