Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Detail) - Successor [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Collateral Variation Margin	$ 71,023
Gross Amounts of Recognized Assets, Derivative Assets	73,826	$ 139,581
Gross Amounts of Recognized Liabilities, Derivative Liabilities	83,409	381,125
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	627	61,839
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	627	61,839
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	73,199	77,742
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	82,782	319,286
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets	0	0
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	81,260	156,925
Net Amount, Derivative Assets	73,199	77,742
Net Amount, Derivative Liabilities	1,522	162,361
Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	54,877	80,407
Gross Amounts of Recognized Liabilities, Derivative Liabilities	2,205,264	2,078,601
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	54,877	80,407
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	2,205,264	2,078,601
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets	0	0
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	0	0
Net Amount, Derivative Assets	54,877	80,407
Net Amount, Derivative Liabilities	2,205,264	2,078,601
Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	73,826	139,045
Gross Amounts of Recognized Liabilities, Derivative Liabilities	81,495	365,776
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	627	61,839
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	627	61,839
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	73,199	77,206
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	80,868	303,937
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	79,912	156,925
Net Amount, Derivative Assets	73,199	77,206
Net Amount, Derivative Liabilities	956	147,012
Interest Rate Swaps [Member] | Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	2,205,264	2,078,601
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	2,205,264	2,078,601
Net Amount, Derivative Liabilities	2,205,264	2,078,601
Futures Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets		536
Gross Amounts of Recognized Liabilities, Derivative Liabilities	1,348
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets		536
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,348
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	1,348
Net Amount, Derivative Assets		536
Net Amount, Derivative Liabilities	0
Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	566	15,349
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	566	15,349
Net Amount, Derivative Liabilities	566	15,349
Currency Swaps [Member] | Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	54,877	80,407
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	54,877	80,407
Net Amount, Derivative Assets	$ 54,877	$ 80,407