Investments - Amortized Cost and Estimated Fair Values of Company's Fixed Maturity and Short-Term Investments Classified as Available-for-Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 290,034	$ 308,790
Gross Unrealized Gains	4,679	1,217
Gross Unrealized Losses Non-OTTI	(4,226)	(7,706)
Fair Value	290,487	302,301
U.S. Government and Agency
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,651	25,102
Gross Unrealized Gains	127	80
Gross Unrealized Losses Non-OTTI	0	(341)
Fair Value	12,778	24,841
Non-U.S. Government
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	90,610	89,631
Gross Unrealized Gains	1,609	42
Gross Unrealized Losses Non-OTTI	(2,276)	(3,889)
Fair Value	89,943	85,784
Corporate
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	175,621	182,773
Gross Unrealized Gains	2,819	1,040
Gross Unrealized Losses Non-OTTI	(1,950)	(3,429)
Fair Value	176,490	180,384
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,946	5,959
Gross Unrealized Gains	59	4
Gross Unrealized Losses Non-OTTI	0	(36)
Fair Value	6,005	5,927
Residential Mortgage-Backed
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	590	665
Gross Unrealized Gains	51	51
Gross Unrealized Losses Non-OTTI	0	(1)
Fair Value	641	715
Asset-Backed
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,616	4,660
Gross Unrealized Gains	14	0
Gross Unrealized Losses Non-OTTI	0	(10)
Fair Value	$ 4,630	$ 4,650