Basis of Preparation and Presentation (Restatement of Unaudited Condensed Consolidated Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts payable	$ (10,716)	$ (7,735)
Net cash provided by operating activities	83,568	65,652
INVESTING ACTIVITIES:
Capital expenditures	(90,249)	(37,636)
Net cash used in investing activities	(68,165)	(29,028)
Supplemental disclosure of cash flow information
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	(13,238)	$ (11,401)
Scenario, Previously Reported [Member]
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts payable	(55,638)
Net cash provided by operating activities	38,646
INVESTING ACTIVITIES:
Capital expenditures	(45,327)
Net cash used in investing activities	(23,243)
Supplemental disclosure of cash flow information
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	(58,160)
Restatement Adjustment [Member]
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts payable	44,922
Net cash provided by operating activities	44,922
INVESTING ACTIVITIES:
Capital expenditures	(44,922)
Net cash used in investing activities	(44,922)
Supplemental disclosure of cash flow information
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	$ 44,922