Schedule IV Reinsurance (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Reinsurance Premiums for Insurance Companies, by Product Segment, Gross Amount	$ 796,253	$ 762,428	$ 891,167
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Ceded to Other Companies	53,700	38,740	94,497
Reinsurance Premiums for Insurance Companies, by Product Segment, Amount Assumed from Other Companies	(3,571)	32,337	29,063
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount	$ 738,982	$ 756,025	$ 825,733
Reinsurance Premiums for Insurance Companies, by Product Segment, Percentage of Amount Assumed to Net	(0.48%)	4.28%	3.52%