Summary Of Significant Accounting Policies (Schedule of Revision to Previous Reported Financial Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash provided by (used in) financing activities	$ 27,218	$ (129,101)	$ 102,620
Net increase (decrease) in cash and cash equivalents	(192)	58	(214)
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts payable	8,192	27,400	(20,306)
Net cash provided by operating activities	265,956	240,130	446,944
INVESTING ACTIVITIES:
Capital expeditures	(255,553)	(186,149)	(561,453)
Net cash used in investing activities	(293,366)	(110,971)	(549,778)
Supplemental disclosure of cash flow information:
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	(20,574)	$ 21,190	$ 105,157
Scenario, Previously Reported [Member]
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts payable	21,824
Net cash provided by operating activities	279,588
INVESTING ACTIVITIES:
Capital expeditures	(269,185)
Net cash used in investing activities	(306,998)
Supplemental disclosure of cash flow information:
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	(6,942)
Revised Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash provided by (used in) financing activities	0
Net increase (decrease) in cash and cash equivalents	0
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts payable	(13,632)
Net cash provided by operating activities	(13,632)
INVESTING ACTIVITIES:
Capital expeditures	13,632
Net cash used in investing activities	13,632
Supplemental disclosure of cash flow information:
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	$ (13,632)