Investments - Summary of Net Investment Income (Detail) - USD ($) $ in Thousands	3 Months Ended								4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Apr. 30, 2013	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Successor [Member]
Investment [Line Items]
Net Realized and Unrealized Gain (Loss) on Trading Securities										$ 3,580	$ 12,615	$ 6,713
Trading Securities, Realized Gain (Loss)										1,702	4,966	(487)
Fixed income securities										147,014	257,404	299,694
Short-term investments										1,528	299	3,092
Loans										306	420	529
Investment expense										(5,982)	(8,786)	(10,477)
Securities available-for-sale and short-term										142,866	249,337	292,838
Other investments										3,580	16,952	8,108
Total net investment income	$ 64,358	$ 64,195	$ 64,753	$ 72,983	$ 66,471	$ 83,581	$ 80,093	$ 70,801		146,446	266,289	300,946
Predecessor [Member]
Investment [Line Items]
Net Realized and Unrealized Gain (Loss) on Trading Securities									$ 369
Trading Securities, Realized Gain (Loss)									0
Fixed income securities									118,097
Short-term investments									677
Loans									146
Investment expense									(2,549)
Securities available-for-sale and short-term									116,371
Other investments									369
Total net investment income									116,740
Gains (losses) on securities held as of reporting date [Member] | Successor [Member]
Investment [Line Items]
Other investments										$ 1,878	$ 7,649	$ 7,200
Gains (losses) on securities held as of reporting date [Member] | Predecessor [Member]
Investment [Line Items]
Other investments									$ 369