Benefit Obligations (Schedule of Nonqualified Pension Plans Funded with Nonqualified Trusts) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Noncurrent Other assets, consisting of insurance contracts	$ 31	$ 35
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent Other assets, consisting of insurance contracts	30	35
Current Other liabilities	20	20
Benefit obligations	221	219
Supplemental Employee Retirement Plan [Member] | Money Market Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Marketable securities, at fair value	$ 17	$ 24