Investment Securities - Schedule of Investments in Accordance with Fair Value Measurement (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Class of Security:
Total fixed-maturity securities	$ 137,016	$ 218,801
Total investments fair value	153,533	263,664
Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities	90,269	124,774
Total investments fair value	106,786	169,637
Fair Value, Inputs, Level 2
Class of Security:
Total fixed-maturity securities	46,747	94,027
Total investments fair value	46,747	94,027
Obligations of U.S. Government Sponsored Enterprises [Member]
Class of Security:
Total fixed-maturity securities	6,480	15,832
Obligations of U.S. Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities	3,021	6,299
Obligations of U.S. Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 2
Class of Security:
Total fixed-maturity securities	3,459	9,533
Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	62,803	81,892
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities	30,474	11,891
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2
Class of Security:
Total fixed-maturity securities	32,329	70,001
Commercial Paper [Member]
Class of Security:
Total fixed-maturity securities	54,997	98,932
Commercial Paper [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities	54,997	98,932
Foreign Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	12,736	22,145
Foreign Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities	1,777	7,652
Foreign Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2
Class of Security:
Total fixed-maturity securities	10,959	14,493
Money Market Funds [Member]
Class of Security:
Total investments fair value	16,517	44,863
Money Market Funds [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total investments fair value	$ 16,517	$ 44,863