Special Purpose Entities, Including Variable Interest Entities - Additional Information (Detail) (USD $)	8 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	1 Months Ended
	Dec. 31, 2013	Dec. 31, 2014	Apr. 30, 2013	Dec. 31, 2012	Apr. 30, 2013
Variable Interest Entities [Line Items]
Fair value of special purpose entities	$ 13,384,000	$ 12,036,000
Consolidated VIE assets	15,988,697,000	15,126,110,000
Consolidated VIE liabilities	15,872,770,000	15,085,685,000
Variable interest entities deconsolidation gain (loss)	15,273,000
Successor [Member]
Variable Interest Entities [Line Items]
Claims on insurance policies issued to these entities	2,747,000	988,000
Predecessor [Member]
Variable Interest Entities [Line Items]
Claims on insurance policies issued to these entities			1,455,000	14,691,000
Asset-Backed Securities and Utility Obligations [Member]
Variable Interest Entities [Line Items]
Weighted average life		6 years 9 months 12 days
Average rating of assets held by sponsored special purpose entities		BBB
Sponsored Variable Interest Entities [Member]
Variable Interest Entities [Line Items]
Number of individual transactions with special purpose entities		15
Number of transactions outstanding with special purpose entities		3
Total principal amount of debt outstanding	461,355,000	457,960,000
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Secured Debt	0	0
Variable Interest Entities [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Amortization Of Variable Interest Entity Intangible Assets	5,015,000
Asset Impairment Charges	76,140
Variable Interest Entities [Member] | Predecessor [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Initial Consolidation, Gain (Loss)					385,291,000
Fair Value Intangible Assets Initially Recorded Upon Consolidation Of Variable Interest Entity			$ 164,520,000		$ 164,520,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					16 years 0 months 0 days
Consolidated Entities [Member]
Variable Interest Entities [Line Items]
Number of consolidated Variable Interest Entities	18	15