Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Detail) (Successor [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Apr. 30, 2013
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	$ 163,683	$ 134,587
Gross Amounts of Recognized Liabilities, Derivative Liabilities	461,610	310,774
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	54,666	56,876
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	54,666	56,876
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	109,017	77,711	121,643
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	406,944	253,898	621,645
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets	0	690
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	170,135	42,555
Net Amount, Derivative Assets	109,017	77,021
Net Amount, Derivative Liabilities	236,809	211,343
Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	2,200,163	1,772,306
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	2,200,163	1,772,306
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	0	0
Net Amount, Derivative Liabilities	2,200,163	1,772,306
Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	161,640	132,250
Gross Amounts of Recognized Liabilities, Derivative Liabilities	385,346	216,287
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	54,666	56,876
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	54,666	56,876
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	106,974	75,374
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	330,680	159,411
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	169,573	42,555
Net Amount, Derivative Assets	106,974	75,374
Net Amount, Derivative Liabilities	161,107	116,856
Interest Rate Swaps [Member] | Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	2,133,268	1,680,834
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	2,133,268	1,680,834
Net Amount, Derivative Liabilities	2,133,268	1,680,834
Futures Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets		2,337
Gross Amounts of Recognized Liabilities, Derivative Liabilities	562
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		2,337
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	562
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets		690
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	562
Net Amount, Derivative Assets		1,647
Net Amount, Derivative Liabilities	0
Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	2,043
Gross Amounts of Recognized Liabilities, Derivative Liabilities	75,502	94,322
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	2,043
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	75,502	94,322
Net Amount, Derivative Assets	2,043
Net Amount, Derivative Liabilities	75,502	94,322
Other Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	200	165
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	200	165
Net Amount, Derivative Liabilities	200	165
Currency Swaps [Member] | Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	66,895	91,472
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	66,895	91,472
Net Amount, Derivative Liabilities	$ 66,895	$ 91,472