Investments - Scheduled Maturities of Company's Fixed Maturity Securities Based on their Fair Values (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Securities with Unrealized Losses, Total	$ 54,261	$ 38,072
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Securities with Unrealized Gains, One year or less	11,150	8,791
Securities with Unrealized Gains, After one through five years	22,241	22,140
Securities with Unrealized Gains, After five through ten years	21,588	24,980
Securities with Unrealized Gains, After ten years	8,566	9,009
Securities with Unrealized Gains, No single maturity date	9,310	12,022
Securities with Unrealized Gains, Total	72,855	76,942
Securities with Unrealized Losses, After one through five years	10,725	12,888
Securities with Unrealized Losses, After five through ten years	37,897	21,450
Securities with Unrealized Losses, After ten years	1,719	1,742
Securities with Unrealized Losses, No single maturity date	1,932
Securities with Unrealized Losses, Total	52,273	36,080
All Fixed Maturity Securities, One year or less	11,150	8,791
All Fixed Maturity Securities, After one through five years	32,966	35,028
All Fixed Maturity Securities, After five through ten years	59,485	46,430
All Fixed Maturity Securities, After ten years	10,285	10,751
All Fixed Maturity Securities, No single maturity date	11,242	12,022
All Fixed Maturity Securities, Total	$ 125,128	$ 113,022