Benefit Obligations (Schedule of Nonqualified Pension Plans Funded with Nonqualified Trusts) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Noncurrent Other assets, consisting of insurance contracts	$ 49	$ 55
Nonqualified Pension Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent Other assets, consisting of insurance contracts	49	55
Current Other liabilities	22	22
Benefit obligations	241	246
Nonqualified Pension Obligations [Member] | Nonqualified Trust Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Marketable securities, at fair value	$ 30	$ 30