Investments - Scheduled Maturities of Company's Fixed Maturity Securities Based on their Fair Values (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Securities with Unrealized Losses, Total	$ 85,959	$ 86,000
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Securities with Unrealized Gains, One year or less	2,701
Securities with Unrealized Gains, After one through five years	7,059
Securities with Unrealized Gains, After ten years	1,754
Securities with Unrealized Gains, No single maturity date	5,046
Securities with Unrealized Gains, Total	16,560
Securities with Unrealized Losses, One year or less	6,574
Securities with Unrealized Losses, After one through five years	23,556
Securities with Unrealized Losses, After five through ten years	33,254
Securities with Unrealized Losses, No single maturity date	21,640
Securities with Unrealized Losses, Total	85,024
All Fixed Maturity Securities, One year or less	9,275
All Fixed Maturity Securities, After one through five years	30,615
All Fixed Maturity Securities, After five through ten years	33,254
All Fixed Maturity Securities, After ten years	1,754
All Fixed Maturity Securities, No single maturity date	26,686
All Fixed Maturity Securities, Total	$ 101,584