Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Interest, Net of Capitalized Interest	$ 275,305	$ 252,030	$ 222,088
Income Taxes, Net of Refunds Received	188,946	(39,293)	41,108
Accrued Capital Expenditures	475,000	388,000	$ 416,000
Non-cash investing and financing activities from property exchanges.	$ 282,000
Non-cash investing and financing activities from the Yates transaction		$ 3,834,000