Fair Value Measurements (Major Categories of Financial Assets and Liabilities Measured on a Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Other Current Assets [Member]
Other assets	$ 123	$ 157
Other Current Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Other assets	123	157
Other Noncurrent Assets [Member]
Other assets	79	92
Other Noncurrent Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Other assets	79	71
Other Noncurrent Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Other assets		21
Other Accrued Liabilities [Member]
Other accrued liabilities	91	100
Other Accrued Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Other accrued liabilities	91	100
Other Liabilities [Member]
Other liabilities	85	165
Other Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Other liabilities	$ 85	165
Renewable Energy [Member] | Other Noncurrent Assets [Member]
Other assets		$ 21