Investment Securities - Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Estimated Fair Values of Fixed-Maturity Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	$ 136,454	$ 217,587
Total fixed-maturity securities, Gross Unrealized Gains	734	1,730
Total fixed-maturity securities, Gross Unrealized Losses	(172)	(516)
Total fixed-maturity securities, Estimated Fair Value	137,016	218,801
Total fixed-maturity securities held in trust, Amortized Cost	55,337	144,909
Total fixed-maturity securities held in trust, Gross Unrealized Gains	527	1,498
Total fixed-maturity securities held in trust, Gross Unrealized Losses	(154)	(503)
Total fixed-maturity securities held in trust, Estimated Fair Value	55,710	145,904
Trading [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Less total unrestricted fixed-maturity securities, Amortized Cost	7,944	7,326
Less total unrestricted fixed-maturity securities, Gross Unrealized Gains	207	232
Less total unrestricted fixed-maturity securities, Gross Unrealized Losses	(18)	(13)
Less total unrestricted fixed-maturity securities, Estimated Fair Value	8,133	7,545
Held to Maturity [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Less total unrestricted fixed-maturity securities, Amortized Cost	73,173	65,352
Less total unrestricted fixed-maturity securities, Estimated Fair Value	73,173	65,352
Obligations of U.S. Government Sponsored Enterprises [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	6,491	15,868
Total fixed-maturity securities, Gross Unrealized Gains	23	127
Total fixed-maturity securities, Gross Unrealized Losses	(34)	(163)
Total fixed-maturity securities, Estimated Fair Value	6,480	15,832
Corporate Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	62,232	80,624
Total fixed-maturity securities, Gross Unrealized Gains	665	1,450
Total fixed-maturity securities, Gross Unrealized Losses	(94)	(182)
Total fixed-maturity securities, Estimated Fair Value	62,803	81,892
Foreign Corporate Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	12,734	22,166
Total fixed-maturity securities, Gross Unrealized Gains	46	149
Total fixed-maturity securities, Gross Unrealized Losses	(44)	(170)
Total fixed-maturity securities, Estimated Fair Value	12,736	22,145
Commercial Paper [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total fixed-maturity securities, Amortized Cost	54,997	98,929
Total fixed-maturity securities, Gross Unrealized Gains		4
Total fixed-maturity securities, Gross Unrealized Losses		(1)
Total fixed-maturity securities, Estimated Fair Value	$ 54,997	$ 98,932