Reinsurance (Details) (USD $)	3 Months Ended									12 Months Ended
	Dec. 31, 2012 Agreement		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 Agreement	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2008	Dec. 31, 2009
Reinsurance [Abstract]
First aggregate layer of loss under aggregate excess of loss agreements, minimum (in hundredths)										4.00%
First aggregate layer of loss under aggregate excess of loss agreements, maximum (in hundredths)										5.00%
Second aggregate layer of loss under aggregate excess of loss agreements, captives, minimum (in hundredths)										5.00%
Second aggregate layer of loss under aggregate excess of loss agreements, captives, maximum (in hundredths)										10.00%
Premium cessions as a percentage of the direct premium, minimum (in hundredths)										25.00%
Premium cessions as a percentage of the direct premium, maximum (in hundredths)										40.00%
Captive's portion of both premiums and losses under quota share arrangement, minimum (in hundredths)										25.00%
Captive's portion of both premiums and losses under quota share arrangement, maximum (in hundredths)										50.00%
New business cede rate, maximum (in hundredths)										25.00%
Reinsurance recoverable on loss reserves	$ 104,848,000					$ 154,607,000				$ 104,848,000	$ 154,607,000	$ 275,290,000		$ 332,227,000
Reinsurance recoverable on loss reserves related to captive agreements	104,000,000					142,000,000				104,000,000	142,000,000
Fair value of trust fund assets under our captive agreements	303,000,000					359,000,000				303,000,000	359,000,000
Fair value of trust fund assets under captive agreements, no reinsurance recoverable on loss reserves	25,000,000					27,000,000				25,000,000	27,000,000
Trust fund assets transferred to us as a result of captive terminations										6,000,000	39,000,000
Number of aggregate excess of loss agreements with special purpose reinsurance companies	3									3
Risk in force amount ceded to date under aggregate excess of loss reinsurance agreements	130,000,000									130,000,000
Number of special purpose reinsurance companies to which risk in force has been ceded	3									3
Number of aggregate excess of loss reinsurance agreements terminated with special purpose reinsurance companies													1
Risk in force amount ceded under remaining aggregate excess of loss reinsurance agreements	800,000									800,000
Premiums earned [Abstract]
Direct										1,065,663,000	1,170,868,000	1,236,949,000
Assumed										2,425,000	3,891,000	3,091,000
Ceded										(34,918,000)	(50,924,000)	(71,293,000)
Net premiums earned	261,705,000	[1]	266,432,000	242,628,000	262,405,000	275,741,000	275,094,000	284,454,000	288,546,000	1,033,170,000	1,123,835,000	1,168,747,000
Losses incurred [Abstract]
Direct										2,115,974,000	1,775,122,000	1,716,538,000
Assumed										6,912,000	5,229,000	4,128,000
Ceded										(55,633,000)	(65,644,000)	(113,125,000)
Net losses incurred	688,636,000	[1]	490,121,000	551,408,000	337,088,000	482,070,000	462,654,000	459,552,000	310,431,000	2,067,253,000	1,714,707,000	1,607,541,000
Unearned premium returned under assumed reinsurance agreement terminated by our Australian writing company										$ 7,000,000

[1] The results for the fourth quarter of 2012 include a loss of approximately $267 million related to our settlement with Freddie Mac and approximately $100 million related to our probable rescission settlement agreements. See Note 20 - "Litigation and Contingencies".