Investments (Details 1) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2013 Number		Dec. 31, 2012 Number
Fixed maturity securities Fair Value
Fixed maturity securities, Fair Value 12 Months or Less	$ 1,512,374		$ 263,571
Fixed maturity securities, Fair Value More than 12 Months	56,514		55,788
Fixed maturity securities, Fair Value, Total	1,568,888		319,359
Fixed maturity securities Gross Unrealized Losses
Fixed maturity securities, Gross Unrealized Losses 12 Months or Less	93,637		5,648
Fixed maturity securities, Gross Unrealized Losses More than 12 Months	6,898		5,532
Fixed maturity securities, Gross Unrealized Losses, Total	100,535		11,180
Number of positions with a gross unrealized loss 12 months or less	509		156
Number of position with gross unrealized loss position more than 12 months	30		43
Number of position with gross unrealized loss position, Total	539		199
Fair value as percentage of total fixed maturities and equity securities fair value less than 12 months	25.10%		4.40%
Fair value as percentage of total fixed maturities and equity securities fair value more than 12 months	0.90%		0.90%
Fair value as percentage of total fixed maturities and equity securities fair value, Total	26.00%		5.30%
Mortgage-backed securities [Member]
Fixed maturity securities Fair Value
Fixed maturity securities, Fair Value 12 Months or Less	112,736		11,006
Fixed maturity securities, Fair Value More than 12 Months	40		50
Fixed maturity securities, Fair Value, Total	112,776		11,056
Fixed maturity securities Gross Unrealized Losses
Fixed maturity securities, Gross Unrealized Losses 12 Months or Less	12,705		124
Fixed maturity securities, Gross Unrealized Losses More than 12 Months	0		1
Fixed maturity securities, Gross Unrealized Losses, Total	12,705		125
Other [Member]
Fixed maturity securities Fair Value
Fixed maturity securities, Fair Value 12 Months or Less	191,183		9,944
Fixed maturity securities, Fair Value More than 12 Months	0		0
Fixed maturity securities, Fair Value, Total	191,183		9,944
Fixed maturity securities Gross Unrealized Losses
Fixed maturity securities, Gross Unrealized Losses 12 Months or Less	14,345		135
Fixed maturity securities, Gross Unrealized Losses More than 12 Months	0		0
Fixed maturity securities, Gross Unrealized Losses, Total	14,345		135
Municipal bonds [Member]
Fixed maturity securities Fair Value
Fixed maturity securities, Fair Value 12 Months or Less	369,099		108,578
Fixed maturity securities, Fair Value More than 12 Months	12,010		3,990
Fixed maturity securities, Fair Value, Total	381,109		112,568
Fixed maturity securities Gross Unrealized Losses
Fixed maturity securities, Gross Unrealized Losses 12 Months or Less	27,759		2,605
Fixed maturity securities, Gross Unrealized Losses More than 12 Months	1,490		43
Fixed maturity securities, Gross Unrealized Losses, Total	29,249		2,648
Foreign government bonds [Member]
Fixed maturity securities Fair Value
Fixed maturity securities, Fair Value 12 Months or Less	5,626		0
Fixed maturity securities, Fair Value More than 12 Months	0		0
Fixed maturity securities, Fair Value, Total	5,626		0
Fixed maturity securities Gross Unrealized Losses
Fixed maturity securities, Gross Unrealized Losses 12 Months or Less	349		0
Fixed maturity securities, Gross Unrealized Losses More than 12 Months	0		0
Fixed maturity securities, Gross Unrealized Losses, Total	349		0
Corporate bonds [Member]
Fixed maturity securities Fair Value
Fixed maturity securities, Fair Value 12 Months or Less	577,369		56,481
Fixed maturity securities, Fair Value More than 12 Months	14,305		26,725
Fixed maturity securities, Fair Value, Total	591,674		83,206
Fixed maturity securities Gross Unrealized Losses
Fixed maturity securities, Gross Unrealized Losses 12 Months or Less	27,982		875
Fixed maturity securities, Gross Unrealized Losses More than 12 Months	3,829		4,075
Fixed maturity securities, Gross Unrealized Losses, Total	31,811		4,950
Other mortgage-backed securities [Member]
Fixed maturity securities Fair Value
Fixed maturity securities, Fair Value 12 Months or Less	222,222		58,218
Fixed maturity securities, Fair Value More than 12 Months	29,125		25,014
Fixed maturity securities, Fair Value, Total	251,347		83,232
Fixed maturity securities Gross Unrealized Losses
Fixed maturity securities, Gross Unrealized Losses 12 Months or Less	7,246		621
Fixed maturity securities, Gross Unrealized Losses More than 12 Months	1,157		1,411
Fixed maturity securities, Gross Unrealized Losses, Total	8,403		2,032
Total fixed maturities securities [Member]
Fixed maturity securities Fair Value
Fixed maturity securities, Fair Value 12 Months or Less	1,478,235		244,227
Fixed maturity securities, Fair Value More than 12 Months	55,480		55,779
Fixed maturity securities, Fair Value, Total	1,533,715		300,006
Fixed maturity securities Gross Unrealized Losses
Fixed maturity securities, Gross Unrealized Losses 12 Months or Less	90,386		4,360
Fixed maturity securities, Gross Unrealized Losses More than 12 Months	6,476		5,530
Fixed maturity securities, Gross Unrealized Losses, Total	96,862		9,890
Equity securities [Member]
Fixed maturity securities Fair Value
Fixed maturity securities, Fair Value 12 Months or Less	34,139	[1]	19,344	[1]
Fixed maturity securities, Fair Value More than 12 Months	1,034	[1]	9	[1]
Fixed maturity securities, Fair Value, Total	35,173	[1]	19,353	[1]
Fixed maturity securities Gross Unrealized Losses
Fixed maturity securities, Gross Unrealized Losses 12 Months or Less	3,251	[1]	1,288	[1]
Fixed maturity securities, Gross Unrealized Losses More than 12 Months	422	[1]	2	[1]
Fixed maturity securities, Gross Unrealized Losses, Total	$ 3,673	[1]	$ 1,290	[1]

[1] Includes nonredeemable (perpetual) preferred stocks, common stocks and closed-end funds.