Accounts Receivable Securitization (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Letters of credit, maximum borrowing capacity	$ 200,000,000
Current borrowing capacity of receivable facility	200,000,000
Letters of Credit Outstanding, Amount	66,055,000
Costs associated with the receivables facility	(1,737,000)	(1,723,000)	(1,986,000)
Eligible accounts receivable	115,000,000	200,000,000
Subordinated Debt	48,945
Borrowings Under Securitization Facility	0	37,846,000
Accounts Receivable—Securitized	0	37,846,000
Decrease in the accounts receivable securitization program	$ (37,846,000)	$ 37,846,000	$ (200,000,000)
AR securitization facility [Member]
Expiration date of receivables facility	Mar. 30, 2017