Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Supplemental Cash Flow Information [Abstract]
Interest (1)	[1]	$ 50,103	$ 77,828
Income Taxes, Net of Refunds Received		3,554	81,960
Interest Costs Capitalized		5,000	7,000
Accrued Capital Expenditures		593,000	$ 415,000
Non-Cash Property Exchanges		9,000
Non-Cash Other Property, Plant and Equipment		$ 48,000

[1] Net of capitalized interest of $5 million and $7 million for the three months ended March 31, 2018 and 2017, respectively.