Reinsurance (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011 entity security segment agreement market subsidiary company policy D transaction counterparty	Sep. 30, 2010	Sep. 30, 2011 subsidiary statement ratingcategory security Y segment entity agreement market company policy D transaction counterparty	Sep. 30, 2010
Reinsurance
Reduction to net income if unearned assumed premiums are recaptured	$ 2,700,000		$ 2,700,000
Number of Ceding Company	1		1
Reduction to net income if additional unearned assumed premiums are recaptured	11,700,000		11,700,000
Commutation gains (losses)		400,000	32,200,000	17,100,000
Increase (Decrease) in Net Unearned Premium Reserve		(500,000)	(20,100,000)	59,900,000
Increase (Decrease) in Net Par		4,081,000,000	(780,000,000)	12,455,000,000
Premiums Written:
Direct	36,900,000	91,700,000	94,300,000	287,400,000
Assumed	(15,300,000)	(14,100,000)	(67,200,000)	(26,000,000)
Ceded	1,500,000	(1,400,000)	5,900,000	56,800,000
Net	23,100,000	76,200,000	33,000,000	318,200,000
Premiums Earned:
Direct	226,900,000	300,700,000	741,800,000	936,800,000
Assumed	4,300,000	20,600,000	35,300,000	57,600,000
Ceded	(20,100,000)	(32,600,000)	(82,000,000)	(94,000,000)
Net	211,073,000	288,767,000	695,118,000	900,437,000
Loss and LAE:
Direct	243,800,000	107,000,000	380,300,000	327,200,000
Assumed	(1,600,000)	7,200,000	(7,400,000)	47,700,000
Ceded	(27,300,000)	(3,400,000)	(59,600,000)	(67,500,000)
Net	$ 214,991,000	$ 110,772,000	$ 313,324,000	$ 307,394,000