Consolidated Variable Interest Entities - Balance Sheets (Details) - Variable Interest Entity, Primary Beneficiary - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Cash and cash equivalents
Variable Interest Entity [Line Items]
Assets	$ 263	$ 350,815
Accounts receivable
Variable Interest Entity [Line Items]
Assets	14,752	17,131
Prepaid expenses and other
Variable Interest Entity [Line Items]
Assets	2,880	2,111
Property, plant and equipment, net
Variable Interest Entity [Line Items]
Assets	2,429,448	1,969,993
Other assets
Variable Interest Entity [Line Items]
Assets	180,447	91,975
Accounts payable
Variable Interest Entity [Line Items]
Liabilities	71,600	35,909
Credit facility borrowings
Variable Interest Entity [Line Items]
Liabilities	91,000	299,000
Other current liabilities
Variable Interest Entity [Line Items]
Liabilities	23,641	15,722
Long-term debt
Variable Interest Entity [Line Items]
Liabilities	493,978	493,401
Other liabilities and credits
Variable Interest Entity [Line Items]
Liabilities	$ 8,910	$ 7,834