Investments - Scheduled Maturities of Company's Fixed Maturity Securities Based on their Fair Values (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Securities with Unrealized Losses, Total	$ 38,072	$ 37,921
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Securities with Unrealized Gains, One year or less	8,791	14,305
Securities with Unrealized Gains, After one through five years	22,140	25,667
Securities with Unrealized Gains, After five through ten years	24,980	20,445
Securities with Unrealized Gains, After ten years	9,009	3,667
Securities with Unrealized Gains, No single maturity date	12,022	15,928
Securities with Unrealized Gains, Total	76,942	80,012
Securities with Unrealized Losses, After one through five years	12,888	10,888
Securities with Unrealized Losses, After five through ten years	21,450	22,836
Securities with Unrealized Losses, After ten years	1,742	4,008
Securities with Unrealized Losses, No single maturity date		189
Securities with Unrealized Losses, Total	36,080	37,921
All Fixed Maturity Securities, One year or less	8,791	14,305
All Fixed Maturity Securities, After one through five years	35,028	36,555
All Fixed Maturity Securities, After five through ten years	46,430	43,281
All Fixed Maturity Securities, After ten years	10,751	7,675
All Fixed Maturity Securities, No single maturity date	12,022	16,117
All Fixed Maturity Securities, Total	$ 113,022	$ 117,933