Investments - Scheduled Maturities of Company's Fixed Maturity Securities Based on their Fair Values (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Securities with Unrealized Losses, Total	$ 17,184	$ 57,573
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Securities with Unrealized Gains, One year or less	2,477
Securities with Unrealized Gains, After one through five years	27,586
Securities with Unrealized Gains, After five through ten years	63,765
Securities with Unrealized Gains, After ten years	8,643
Securities with Unrealized Gains, No single maturity date	5,918
Securities with Unrealized Gains, Total	108,389
Securities with Unrealized Losses, After one through five years	7,823
Securities with Unrealized Losses, No single maturity date	304
Securities with Unrealized Losses, Total	8,127
Securities with No Unrealized Gains or Losses, One year or less	1,025
Securities with No Unrealized Gains or Losses, Total	1,025
All Fixed Maturity Securities, One year or less	3,502
All Fixed Maturity Securities, After one through five years	35,409
All Fixed Maturity Securities, After five through ten years	63,765
All Fixed Maturity Securities, After ten years	8,643
All Fixed Maturity Securities, No single maturity date	6,222
All Fixed Maturity Securities, Total	$ 117,541