Investment Securities - Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Estimated Fair Values of Fixed-Maturity Securities (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	$ 105,886	$ 60,202
Total fixed-maturity securities, Gross Unrealized Gains	149	590
Total fixed-maturity securities, Gross Unrealized Losses	(30)	(151)
Total fixed-maturity securities, Estimated Fair Value	106,005	60,641
Unrestricted Fixed-Maturity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	73,834	7,895
Total fixed-maturity securities, Gross Unrealized Gains	33	179
Total fixed-maturity securities, Gross Unrealized Losses	(2)	(11)
Total fixed-maturity securities, Estimated Fair Value	73,865	8,063
Fixed-Maturity Securities Held in Trust [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	32,052	52,307
Total fixed-maturity securities, Gross Unrealized Gains	116	411
Total fixed-maturity securities, Gross Unrealized Losses	(28)	(140)
Total fixed-maturity securities, Estimated Fair Value	32,140	52,578
Obligations of U.S. Government Sponsored Enterprises [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	74,364	6,491
Total fixed-maturity securities, Gross Unrealized Gains	19	12
Total fixed-maturity securities, Gross Unrealized Losses	(3)	(28)
Total fixed-maturity securities, Estimated Fair Value	74,380	6,475
Corporate Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	21,493	41,018
Total fixed-maturity securities, Gross Unrealized Gains	108	531
Total fixed-maturity securities, Gross Unrealized Losses	(12)	(65)
Total fixed-maturity securities, Estimated Fair Value	21,589	41,484
Foreign Corporate Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	10,029	12,693
Total fixed-maturity securities, Gross Unrealized Gains	22	47
Total fixed-maturity securities, Gross Unrealized Losses	(15)	(58)
Total fixed-maturity securities, Estimated Fair Value	$ 10,036	$ 12,682