Investments - Scheduled Maturities of Company's Fixed Maturity Securities Based on their Fair Values (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Investments Debt And Equity Securities [Abstract]
Securities with Unrealized Gains, One year or less	$ 10,260	$ 9,380
Securities with Unrealized Gains, After one through five years	28,724	34,460
Securities with Unrealized Gains, After five through ten years	17,080	25,230
Securities with Unrealized Gains, After ten years	6,756	10,770
Securities with Unrealized Gains, No single maturity date	20,605	23,833
Securities with Unrealized Gains, Total	83,425	103,673
Securities with Unrealized Losses, One year or less
Securities with Unrealized Losses, After one through five years	13,579	11,518
Securities with Unrealized Losses, After five through ten years	20,409	15,181
Securities with Unrealized Losses, After ten years	2,749
Securities with Unrealized Losses, No single maturity date	378	336
Securities with Unrealized Losses, Total	37,115	27,035
Securities with No Unrealized Gains or Losses, One year or less	1,585	5
Securities with No Unrealized Gains or Losses, After one through five years
Securities with No Unrealized Gains or Losses, After five through ten years
Securities with No Unrealized Gains or Losses, After ten years
Securities with No Unrealized Gains or Losses, No single maturity date
Securities with No Unrealized Gains or Losses, Total	1,585	5
All Fixed Maturity Securities, One year or less	11,845	9,385
All Fixed Maturity Securities, After one through five years	42,303	45,978
All Fixed Maturity Securities, After five through ten years	37,489	40,411
All Fixed Maturity Securities, After ten years	9,505	10,770
All Fixed Maturity Securities, No single maturity date	20,983	24,169
All Fixed Maturity Securities, Total	$ 122,125	$ 130,713