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, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 238,617	$ 243,302
Gross Unrealized Holding Gains	3,488	3,501
Gross Unrealized Holding Losses Non-OTTI	(796)	(439)
Fair Value	241,309	246,364
U.S. Government and Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,993	28,050
Gross Unrealized Holding Gains	266	303
Gross Unrealized Holding Losses Non-OTTI	(32)	(10)
Fair Value	14,227	28,343
Non-U.S. Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	81,906	84,443
Gross Unrealized Holding Gains	1,608	1,871
Gross Unrealized Holding Losses Non-OTTI	(616)	(22)
Fair Value	82,898	86,292
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	86,697	76,942
Gross Unrealized Holding Gains	1,490	1,221
Gross Unrealized Holding Losses Non-OTTI	(115)	(259)
Fair Value	88,072	77,904
Residential Mortgage-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,454	17,523
Gross Unrealized Holding Gains	97	102
Gross Unrealized Holding Losses Non-OTTI	(3)	(118)
Fair Value	4,548	17,507
Asset-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	51,567	36,344
Gross Unrealized Holding Gains	27	4
Gross Unrealized Holding Losses Non-OTTI	(30)	(30)
Fair Value	$ 51,564	$ 36,318