Credit Facility (Summary Of Outstanding Letters Of Credit And/Or Borrowings) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Line of Credit Facility [Line Items]
Commitment	$ 150,000	$ 150,000
In use	5,020	5,020
Citibank Holdings Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment	150,000	150,000
Letters Of Credit [Member]
Line of Credit Facility [Line Items]
In use	$ 5,020	$ 5,020
Maturity/Expiry Date	Dec. 31, 2012	Dec. 31, 2012