Significant Non-Cash Investing Activities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Other Significant Noncash Transactions [Line Items]
Outstanding receivables from outside parties for the funding of capital expenditures	$ 390,525		$ 363,104
Purchases of property and equipment accrued in accounts payable	45,100	$ 27,800
Accounts receivable - grants from outside parties
Other Significant Noncash Transactions [Line Items]
Outstanding receivables from outside parties for the funding of capital expenditures	$ 20,949	$ 25,900	$ 32,076