Fair Value Measurements - Summary of Gains and Losses (Realized and Unrealized) Relating to Level 3 Assets and Liabilities Included in Earnings (Detail) (USD $) In Thousands, unless otherwise specified	8 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014	Apr. 30, 2013	Dec. 31, 2012
Successor [Member] | Variable Interest Entity [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	$ (636,043)	$ 1,256,740
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	(655,964)	1,261,927
Predecessor [Member] | Variable Interest Entity [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period			1,146,256	702,496
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			1,146,256	702,977
Net Investment Income [Member] | Successor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	1,870	11,057
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	0	0
Net Investment Income [Member] | Predecessor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period			(33)	(3)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			0	0
Realized Gains Or (Losses) and Other Settlements On Credit Derivative Contracts [Member] | Successor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	9,778	3,043
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	0	0
Realized Gains Or (Losses) and Other Settlements On Credit Derivative Contracts [Member] | Predecessor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period			3,444	13,713
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			0	0
Unrealized Gains Or (Losses) On Credit Derivative Contracts [Member] | Successor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	183,091	20,863
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	66,639	15,789
Unrealized Gains Or (Losses) On Credit Derivative Contracts [Member] | Predecessor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period			(63,828)	(22,932)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			(63,840)	(35,331)
Interest Rate Swap [Member] | Successor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	24,797	(69,298)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	24,797	(69,298)
Interest Rate Swap [Member] | Predecessor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period			(28,162)	(70,415)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			(28,162)	(78,505)
Other Income or (Loss) [Member] | Successor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	(677)	(1,348)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	(677)	(1,348)
Other Income or (Loss) [Member] | Predecessor [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period			(496)	98,488
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			$ (496)	$ (2,222)