Accounts Receivable Securitization (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 AR securitization facility [Member]	Sep. 30, 2012 AR securitization facility [Member]	Sep. 30, 2013 AR securitization facility [Member]	Sep. 30, 2012 AR securitization facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity			$ 200,000		$ 200,000
Current borrowing capacity of receivable facility			200,000		200,000
Letters of credit amount outstanding			155,636		155,636
Costs associated with the receivables facility			416	420	1,328	1,276
Expiration date of receivables facility					Mar. 30, 2017
Accounts Receivable - Securitized	44,364	37,846
Increase (Decrease) in Accounts Receivable from Securitization	$ 6,518