Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017
Supplemental Cash Flow Information [Abstract]
Interest (1)	[1]	$ 133,148	$ 136,733
Income Taxes, Net of Refunds Received		62,777	98,157
Interest Costs Capitalized		11,000	14,000
Accrued Capital Expenditures		724,000	488,000
Non-Cash Property Exchanges		83,000	$ 154,000
Non-Cash Other Property, Plant and Equipment		$ 48,000

[1] Net of capitalized interest of $11 million and $14 million for the six months ended June 30, 2018 and 2017, respectively.