Investments - Fair Value and Gross Unrealized Losses of Fixed Maturity Securities in Continuous Unrealized Loss Position for Greater than 12 Months (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014 Security	Dec. 31, 2013 Security
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	9	7
Fair Value	$ 20,567	$ 13,980
12 months or longer, Gross Unrealized Losses	(592)	(1,270)
Less Than or Equal to 10% [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	9	7
Fair Value	20,567	13,980
12 months or longer, Gross Unrealized Losses	$ (592)	$ (1,270)