Investments - Summary of Net Investment Income (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Investment [Line Items]
Fixed income securities	$ 81,831	$ 67,293	$ 207,358	$ 197,506
Short-term investments	194	85	1,124	186
Loans	97	113	273	338
Investment expense	(2,592)	(1,872)	(6,875)	(6,801)
Securities available-for-sale and short-term	79,530	65,619	201,880	191,229
Other investments	11,387	(1,424)	20,616	10,702
Total net investment income	90,917	64,195	222,496	201,931
Gains (losses) on securities held as of reporting date [Member]
Investment [Line Items]
Net Realized and Unrealized Gain (Loss) on Trading Securities	10,197	(2,549)	17,145	7,493
Trading Securities, Realized Gain (Loss)	1,859	933	5,268	7,534
Other investments	$ 8,338	$ (3,482)	$ 11,877	$ (41)