Consolidated Variable Interest Entities (Balance Sheets) (Details) - Variable Interest Entity, Primary Beneficiary - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Cash and cash equivalents
Variable Interest Entity [Line Items]
Assets	$ 84,356	$ 350,815
Accounts receivable
Variable Interest Entity [Line Items]
Assets	15,749	17,131
Prepaid expenses and other
Variable Interest Entity [Line Items]
Assets	2,341	2,111
Property, plant and equipment, net
Variable Interest Entity [Line Items]
Assets	2,276,474	1,969,993
Other assets
Variable Interest Entity [Line Items]
Assets	156,033	91,975
Accounts payable
Variable Interest Entity [Line Items]
Liabilities	71,818	35,909
Credit facility borrowings
Variable Interest Entity [Line Items]
Liabilities	0	299,000
Other current liabilities
Variable Interest Entity [Line Items]
Liabilities	43,543	15,722
Long-term debt
Variable Interest Entity [Line Items]
Liabilities	493,786	493,401
Other liabilities and credits
Variable Interest Entity [Line Items]
Liabilities	$ 9,333	$ 7,834