Income Taxes (Components Of Net Deferred Income Tax Liability (Asset) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax liabilities [Abstract]
Property, plant and equipment basis differences	$ 2,182	$ 2,022
Intangibles	18	140
Deferred revenue/expense	66	8
Other, net		4
Gross deferred income tax liability	2,266	2,174
Deferred income tax assets [Abstract]
Pension liability	209	176
Tax operating loss carryforward	1,027	960
Employee benefits	176	192
Interest expense deduction limitation carryforward	104
Accrued expenses	41	23
Lease obligations	33	39
Tax credits	37	43
Allowance for doubtful accounts	26	7
Other, net	1	2
Gross deferred income tax asset	1,654	1,442
Less: Valuation allowance	(497)	(407)
Net deferred income tax asset	1,157	1,035
Net deferred income tax liability	$ 1,109	$ 1,139