Significant Non-Cash Investing Activities (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Other Significant Noncash Transactions [Line Items]
Accounts receivable, gross, current	$ 329,812,000		$ 329,208,000
Purchases of property and equipment accrued in accounts payable but not yet paid	12,800,000	14,600,000
Accounts receivable - grants from outside parties [Member]
Other Significant Noncash Transactions [Line Items]
Accounts receivable, gross, current	$ 23,052,000	$ 20,900,000	$ 33,003,000