Consolidated Variable Interest Entities - Balance Sheets (Details) - Variable Interest Entity, Primary Beneficiary - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Cash and cash equivalents
Variable Interest Entity [Line Items]
Assets	$ 42,768	$ 60,453
Accounts receivable
Variable Interest Entity [Line Items]
Assets	21,630	20,662
Prepaid expenses and other
Variable Interest Entity [Line Items]
Assets	1,582	5,745
Property, plant and equipment, net
Variable Interest Entity [Line Items]
Assets	2,632,465	2,578,834
Other assets
Variable Interest Entity [Line Items]
Assets	258,779	206,104
Accounts payable
Variable Interest Entity [Line Items]
Liabilities	43,531	35,831
Other current liabilities
Variable Interest Entity [Line Items]
Liabilities	61,807	32,242
Long-term debt
Variable Interest Entity [Line Items]
Liabilities	986,137	985,732
Other liabilities and credits
Variable Interest Entity [Line Items]
Liabilities	$ 10,258	$ 9,562