SCHEDULE VI - Supplemental Information Concerning Property-Casualty Insurance Operations (Details) ([ConsolidatedPropertyAndCasualtyInsuranceEntityMember], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
[ConsolidatedPropertyAndCasualtyInsuranceEntityMember]
Supplemental Information Concerning Property-Casualty Insurance Operations [Line Items]
Deferred policy acquisition costs	$ 363,188	$ 339,094	$ 369,081
Liability for unpaid losses and loss expenses	10,709,371	11,273,091	10,666,604
Unearned premiums	1,517,358	1,433,525	1,578,754
Premiums earned	3,691,341	3,855,606	4,032,906
Losses and loss expenses incurred	2,157,629	3,722,309	2,659,991
Amortization of deferred policy acquisition costs	821,022	821,477	856,257
Paid losses and loss expenses	2,705,062	2,990,559	2,579,018
Premiums written	$ 3,774,474	$ 3,700,575	$ 3,962,677