Investments (Summarizes the Market Value of those Investments in an Unrealized Loss Position for Periods Less Than and Greater Than 12 Months) (Details) (USD $) In Thousands	Dec. 31, 2010
Gross Fair Value	$ 50,620
Unrealized Loss	(2,594)
Less Than 12 Months [Member]
Gross Fair Value	39,622
Unrealized Loss	(1,169)
Non-U.S. Government and Government Agencies [Member] | Less Than 12 Months [Member]
Gross Fair Value	34,204
Unrealized Loss	(1,116)
States, Municipalities and Political Subdivisions [Member] | Less Than 12 Months [Member]
Gross Fair Value	472
Unrealized Loss	(13)
Corporate Debt, Financial Institutions [Member] | Less Than 12 Months [Member]
Gross Fair Value	2,796
Unrealized Loss	(38)
Corporate Debt, Industrials [Member] | Less Than 12 Months [Member]
Gross Fair Value	2,150
Unrealized Loss	(2)
More Than 12 Months [Member]
Gross Fair Value	10,998
Unrealized Loss	(1,425)
Non-U.S. Government and Government Agencies [Member] | More Than 12 Months [Member]
Gross Fair Value	10,998
Unrealized Loss	$ (1,425)