Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair values of fixed-maturity securities
Fixed maturity securities amortized cost	$ 341,203	$ 298,978
Total fixed-maturity securities, Gross Unrealized Gains	6,802	6,442
Total fixed-maturity securities, Gross Unrealized Losses	(438)	(1,375)
Total fixed-maturity securities, Estimated Fair Value	347,567	304,045
Less total unrestricted fixed-maturity securities Amortized Cost	63,567	5,348
Less total unrestricted fixed-maturity securities, Gross unrealized gains	377	151
Less total unrestricted fixed-maturity securities, Gross unrealized losses	(53)	(9)
Less total unrestricted fixed-maturity securities, Estimated Fair Value	63,891	5,490
Total fixed-maturity securities held in trust, Amortized Cost	277,636	293,630
Total fixed-maturity securities held in trust, Gross Unrealized Gains	6,425	6,291
Total fixed-maturity securities held in trust, Gross Unrealized Losses	(385)	(1,366)
Total fixed-maturity securities held in trust, Estimated Fair Value	283,676	298,555
U.S. Treasury securities [Member]
Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair values of fixed-maturity securities
Fixed maturity securities amortized cost	250	250
Total fixed-maturity securities, Estimated Fair Value	250	250
Obligations of U.S. government sponsored enterprises [Member]
Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair values of fixed-maturity securities
Fixed maturity securities amortized cost	128,886	122,874
Total fixed-maturity securities, Gross Unrealized Gains	1,935	2,029
Total fixed-maturity securities, Gross Unrealized Losses	(147)	(267)
Total fixed-maturity securities, Estimated Fair Value	130,674	124,636
Corporate debt securities [Member]
Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair values of fixed-maturity securities
Fixed maturity securities amortized cost	129,447	129,916
Total fixed-maturity securities, Gross Unrealized Gains	4,224	3,791
Total fixed-maturity securities, Gross Unrealized Losses	(135)	(845)
Total fixed-maturity securities, Estimated Fair Value	133,536	132,862
Commercial Paper [Member]
Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair values of fixed-maturity securities
Fixed maturity securities amortized cost	29,966
Total fixed-maturity securities, Gross Unrealized Gains	7
Total fixed-maturity securities, Gross Unrealized Losses	(3)
Total fixed-maturity securities, Estimated Fair Value	29,970
Foreign corporate debt securities [Member]
Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair values of fixed-maturity securities
Fixed maturity securities amortized cost	33,045	26,800
Total fixed-maturity securities, Gross Unrealized Gains	560	546
Total fixed-maturity securities, Gross Unrealized Losses	(25)	(117)
Total fixed-maturity securities, Estimated Fair Value	33,580	27,229
Commercial mortgage-backed securities [Member]
Schedule of amortized cost, gross unrealized gains, gross unrealized losses and estimated fair values of fixed-maturity securities
Fixed maturity securities amortized cost	19,609	19,138
Total fixed-maturity securities, Gross Unrealized Gains	76	76
Total fixed-maturity securities, Gross Unrealized Losses	(128)	(146)
Total fixed-maturity securities, Estimated Fair Value	$ 19,557	$ 19,068