Investment Securities - Schedule of Investments in Accordance with Fair Value Measurement (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Class of Security:
Total fixed-maturity securities	$ 147,040	$ 218,801
Total investments fair value	155,004	263,664
Obligations of U.S. Government Sponsored Enterprises [Member]
Class of Security:
Total fixed-maturity securities	8,507	15,832
Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	68,201	81,892
Commercial Paper [Member]
Class of Security:
Total fixed-maturity securities	51,481	98,932
Foreign Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	18,851	22,145
Money Market Funds [Member]
Class of Security:
Total investments fair value	7,964	44,863
Level 1 [Member]
Class of Security:
Total fixed-maturity securities	92,263	124,774
Total investments fair value	100,227	169,637
Level 1 [Member] | Obligations of U.S. Government Sponsored Enterprises [Member]
Class of Security:
Total fixed-maturity securities	3,029	6,299
Level 1 [Member] | Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	29,957	11,891
Level 1 [Member] | Commercial Paper [Member]
Class of Security:
Total fixed-maturity securities	51,481	98,932
Level 1 [Member] | Foreign Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	7,796	7,652
Level 1 [Member] | Money Market Funds [Member]
Class of Security:
Total investments fair value	7,964	44,863
Level 2 [Member]
Class of Security:
Total fixed-maturity securities	54,777	94,027
Total investments fair value	54,777	94,027
Level 2 [Member] | Obligations of U.S. Government Sponsored Enterprises [Member]
Class of Security:
Total fixed-maturity securities	5,478	9,533
Level 2 [Member] | Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	38,244	70,001
Level 2 [Member] | Foreign Corporate Debt Securities [Member]
Class of Security:
Total fixed-maturity securities	$ 11,055	$ 14,493