Investment Securities - Schedule of Investments in Accordance with Fair Value Measurement (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	$ 49,280	$ 76,831
Total investments fair value	73,717	81,379
Money Market Funds [Member]
Class of securities:
Money market funds	24,437	4,548
Level 1
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	36,002	60,567
Total investments fair value	60,439	65,115
Level 1 | Money Market Funds [Member]
Class of securities:
Money market funds	24,437	4,548
Level 2
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	13,278	16,264
Total investments fair value	13,278	16,264
U.S. Government Treasury Securities [Member]
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	249	249
U.S. Government Treasury Securities [Member] | Level 1
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	249	249
Obligations of U.S. Government Sponsored Enterprises [Member]
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	34,416	59,371
Obligations of U.S. Government Sponsored Enterprises [Member] | Level 1
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	24,497	47,489
Obligations of U.S. Government Sponsored Enterprises [Member] | Level 2
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	9,919	11,882
Corporate Debt Securities [Member]
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	9,848	11,415
Corporate Debt Securities [Member] | Level 1
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	6,489	7,033
Corporate Debt Securities [Member] | Level 2
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	3,359	4,382
Foreign Corporate Debt Securities [Member]
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	4,767	5,796
Foreign Corporate Debt Securities [Member] | Level 1
Class of securities:
Total fixed-maturity securities, Estimated Fair Value	$ 4,767	$ 5,796