Investment Securities - Schedule of Investments in Accordance with Fair Value Measurement (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Class of Security:
Total fixed maturity securities	$ 218,801	$ 277,469
Total investments fair value	263,664	311,097
Obligations of U.S. Government Sponsored Enterprises [Member]
Class of Security:
Total fixed maturity securities	15,832	98,363
Corporate Debt Securities [Member]
Class of Security:
Total fixed maturity securities	81,892	94,974
Commercial Paper [Member]
Class of Security:
Total fixed maturity securities	98,932	54,948
Foreign Corporate Debt Securities [Member]
Class of Security:
Total fixed maturity securities	22,145	18,666
Money Market Funds [Member]
Class of Security:
Total investments fair value	44,863	33,628
Commercial Mortgage-Backed Securities [Member]
Class of Security:
Total fixed maturity securities		10,518
Level 1 [Member]
Class of Security:
Total fixed maturity securities	124,774	90,144
Total investments fair value	169,637	123,772
Level 1 [Member] | Obligations of U.S. Government Sponsored Enterprises [Member]
Class of Security:
Total fixed maturity securities	6,299	11,362
Level 1 [Member] | Corporate Debt Securities [Member]
Class of Security:
Total fixed maturity securities	11,891	22,833
Level 1 [Member] | Commercial Paper [Member]
Class of Security:
Total fixed maturity securities	98,932	54,948
Level 1 [Member] | Foreign Corporate Debt Securities [Member]
Class of Security:
Total fixed maturity securities	7,652	1,001
Level 1 [Member] | Money Market Funds [Member]
Class of Security:
Total investments fair value	44,863	33,628
Level 1 [Member] | Commercial Mortgage-Backed Securities [Member]
Class of Security:
Total fixed maturity securities
Level 2 [Member]
Class of Security:
Total fixed maturity securities	94,027	187,325
Total investments fair value	94,027	187,325
Level 2 [Member] | Obligations of U.S. Government Sponsored Enterprises [Member]
Class of Security:
Total fixed maturity securities	9,533	87,001
Level 2 [Member] | Corporate Debt Securities [Member]
Class of Security:
Total fixed maturity securities	70,001	72,141
Level 2 [Member] | Commercial Paper [Member]
Class of Security:
Total fixed maturity securities
Level 2 [Member] | Foreign Corporate Debt Securities [Member]
Class of Security:
Total fixed maturity securities	14,493	17,665
Level 2 [Member] | Money Market Funds [Member]
Class of Security:
Total investments fair value
Level 2 [Member] | Commercial Mortgage-Backed Securities [Member]
Class of Security:
Total fixed maturity securities		10,518
Level 3 [Member]
Class of Security:
Total fixed maturity securities
Total investments fair value
Level 3 [Member] | Obligations of U.S. Government Sponsored Enterprises [Member]
Class of Security:
Total fixed maturity securities
Level 3 [Member] | Corporate Debt Securities [Member]
Class of Security:
Total fixed maturity securities
Level 3 [Member] | Commercial Paper [Member]
Class of Security:
Total fixed maturity securities
Level 3 [Member] | Foreign Corporate Debt Securities [Member]
Class of Security:
Total fixed maturity securities
Level 3 [Member] | Money Market Funds [Member]
Class of Security:
Total investments fair value
Level 3 [Member] | Commercial Mortgage-Backed Securities [Member]
Class of Security:
Total fixed maturity securities