Fair Value Measurements - Summary of Information about Described Model Inputs Used to Determine Fair Value of Each Class of Credit Derivatives (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	$ 294,376	$ 285,261
Notional outstanding	933,064	970,883
Other Contracts [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Notional outstanding		$ 58,482
Weighted average life (WAL) in years		2 months
Weighted average credit rating		A+
CVA percentage		0.09%
Fair value of derivative liabilities		$ 9
Successor [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Notional outstanding	933,064	970,883
Successor [Member] | CLO [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Notional outstanding	$ 284,411	$ 295,253
Weighted average reference obligation price	$ 98.9	$ 98.4
Weighted average life (WAL) in years	11 months	1 year 1 month
Weighted average credit rating	AA	AA
Weighted average relative change ratio	36.30%	36.30%
CVA percentage	6.50%	8.34%
Fair value of derivative liabilities	$ 1,064	$ 1,837
Successor [Member] | Other [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Notional outstanding	$ 648,653	$ 617,148
Weighted average reference obligation price	$ 90.3	$ 85.2
Weighted average life (WAL) in years	5 years 11 months	6 years 1 month
Weighted average credit rating	BBB+	BBB+
Weighted average relative change ratio	33.30%	33.30%
CVA percentage	17.87%	23.34%
Fair value of derivative liabilities	$ 20,865	$ 32,697
Real Estate [Member] | Successor [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	58,266	59,719
Hedge Funds, Multi-strategy [Member] | Successor [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	49,218	35,464
Interest Rate Contract [Member] | Successor [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	95,503	99,579
Illiquid Investments [Member] | Successor [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	$ 43,716	$ 44,754