Debt Credit Facility (Details) (USD $) In Thousands, unless otherwise specified				9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Revolving Credit Facility [Member] Long-term Debt [Member]	Sep. 30, 2013 Letter of Credit [Member] Long-term Debt [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 137,500
Line of Credit Facility, Remaining Borrowing Capacity			44,255
Line of Credit Facility, Amount Outstanding	16,725	0	16,725
Line Of Credit Facility Additional Borrowings Under Letter Of Credit Sub Facility				80,000
Letters of Credit Outstanding, Amount				$ 70,545