Losses and Loss Expenses (Details) - Asbestos and Environmental Exposures (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of opening and closing unpaid losses and loss expenses related to asbestos and environmental exposure claims:
Net unpaid losses and loss expenses at beginning of year	$ 77,778,000	$ 84,075,000	$ 100,922,000
Net incurred losses and loss expenses	6,558,000	(41,000)	(130,000)
Less net paid losses and loss expenses	6,021,000	6,256,000	16,718,000
Net increase (decrease) in unpaid losses and loss expenses	537,000	(6,297,000)	(16,848,000)
Net unpaid losses and loss expenses at end of year	78,315,000	77,778,000	84,075,000
Unpaid losses and loss expenses recoverable at end of year	123,799,000	134,323,000	142,037,000
Gross unpaid losses and loss expenses at end of year	202,114,000	212,101,000	226,112,000
Reserves for incurred but not reported losses, net of reinsurance	$ 52,200,000	$ 47,200,000	$ 54,900,000