Investment Securities - Schedule of Investments in Accordance with Fair Value Measurement (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Class of Security:
Total fixed-maturity securities	$ 60,641	$ 218,801
Total investments fair value	149,492	263,664
Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities	20,770	124,774
Total investments fair value	109,621	169,637
Fair Value, Inputs, Level 2
Class of Security:
Total fixed-maturity securities	39,871	94,027
Total investments fair value	39,871	94,027
Obligations of U.S. Government Sponsored Enterprises [Member]
Class of Security:
Total fixed-maturity securities	6,475	15,832
Obligations of U.S. Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities	3,009	6,299
Obligations of U.S. Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 2
Class of Security:
Total fixed-maturity securities	3,466	9,533
Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	41,484	81,892
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities	14,939	11,891
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2
Class of Security:
Total fixed-maturity securities	26,545	70,001
Commercial Paper [Member]
Class of Security:
Total fixed-maturity securities		98,932
Commercial Paper [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities		98,932
Foreign Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	12,682	22,145
Foreign Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total fixed-maturity securities	2,822	7,652
Foreign Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2
Class of Security:
Total fixed-maturity securities	9,860	14,493
Money Market Funds [Member]
Class of Security:
Total investments fair value	88,851	44,863
Money Market Funds [Member] | Fair Value, Inputs, Level 1
Class of Security:
Total investments fair value	$ 88,851	$ 44,863