Liability for Unpaid Loss and Loss Adjustmene Expense (Details Textuals) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Liability for Unpaid Loss and Loss Adjustment Expense
Net catastrophe losses recognized during the year.	$ 52,400,000	$ 103,900,000	$ 22,500,000
Reserve releases included in loss development	21,400,000	8,100,000	12,600,000
Net favorable development for international segment	10,100,000
Adverse development from international surety and credit line	$ 43,300,000