Acquisitions - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Mar. 07, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017
Identifiable assets acquired:
Goodwill		$ 57,736	$ 60,300	$ 0
Identifiable liabilities assumed:
Less: noncontrolling interests		(11,113)			$ (325,600)
Net assets acquired, net of cash and restricted cash acquired		$ 263,558			$ 190,958
Tsugaru Holdings [Member]
Business Acquisition [Line Items]
Consideration	$ 282,548
Identifiable assets acquired:
Cash and cash equivalents	10,100
Restricted cash, current	8,325
Trade receivables	3,005
Prepaid expenses	2,207
Other current assets	8,368
Major equipment advances	1,240
Restricted cash, noncurrent	565
Deferred financing costs, net	1,337
Property, plant and equipment	263,281
Construction in progress	180,949
Land	112
Goodwill	60,302
Finite lived intangible assets	103,170
Other noncurrent assets	3,270
Identifiable liabilities assumed:
Accounts payable and other accrued liabilities	(6,607)
Accrued interest	(474)
Accrued construction costs	(4,128)
Contingent liabilities, current	(16,249)
Current portion of long-term debt	(7,511)
Other current liabilities	(22,094)
Long-term debt	(173,828)
Deferred tax liabilities	(67,179)
Asset retirement obligations	(39,872)
Finite lived intangible liability	(9,252)
Derivative liabilities	(5,376)
Total consideration before non-controlling interest	293,661
Less: noncontrolling interests	(11,113)
Net assets acquired, net of cash and restricted cash acquired	$ 282,548