Schedule VI Supplementary Reinsurance Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Net loss and loss adjustment expenses, Current Year	$ 1,239,016	$ 1,028,855	$ 787,967
Net loss and loss adjustment expenses, Prior Year	23,332	14,199	(32,845)
Paid loss and loss adjustment expenses	$ 1,015,309	$ 880,004	$ 631,334