Benefit Obligations (Schedule of Nonqualified Pension Plans Funded with Nonqualified Trusts) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Noncurrent Other assets, consisting of insurance contracts	$ 35	$ 37
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent Other assets, consisting of insurance contracts	35	37
Current Other liabilities	20	21
Benefit obligations	219	213
Supplemental Employee Retirement Plan [Member] | Money Market Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Marketable securities, at fair value	$ 24	$ 31