Fair Value Measurements - Summary of Information about Described Model Inputs Used to Determine Fair Value of Each Class of Credit Derivatives (Detail) - Successor [Member] - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	$ 452,032	$ 450,307
Notional outstanding	455,792	737,380
Other [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Notional outstanding	$ 455,792	$ 737,380
Weighted average reference obligation price	$ 94.0	$ 93.5
Weighted average life (WAL) in years	5 years 8 months	5 years 2 months
Weighted average credit rating	A-	A-
Weighted average relative change ratio	29.50%	31.60%
CVA percentage	13.31%	11.14%
Fair value of derivative liabilities	$ 9,006	$ 15,349
Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	33,218	33,303
Hedge Funds, Multi-strategy [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	49,292	53,985
Interest Rate Contract [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	223,364	261,315
Illiquid Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Other investments	$ 63,027	$ 39,068
Asset-backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs Coupon Rate	5.97%	5.93%
Fair Value Inputs Maturity	17 years 5 months 10 days	17 years 8 months 25 days
Fair Value Inputs Yield	0.00%	13.50%
Variable Interest Entity, Primary Beneficiary [Member] | US Commercial ABS Transaction [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs Coupon Rate	5.88%	5.88%
Fair Value Inputs Maturity	20 years 4 months 5 days	20 years 8 months 68 days
Fair Value Inputs Yield	5.96%	5.86%
Variable Interest Entity, Primary Beneficiary [Member] | European Transactions [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs Coupon Rate	0.43%	0.46%
Fair Value Inputs Maturity	15 years 9 months 15 days	16 years 1 month 28 days
Fair Value Inputs Yield	4.79%	4.95%