Fair Value Measurements (Major Categories of Financial Assets and Liabilities Measured on a Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Other Current Assets [Member]
Other assets	$ 173	$ 157
Other Current Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Other assets	173	157
Other Noncurrent Assets [Member]
Other assets	110	92
Other Noncurrent Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Other assets	91	71
Other Noncurrent Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Other assets	19	21
Other Accrued Liabilities [Member]
Other accrued liabilities	143	100
Other Accrued Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Other accrued liabilities	143	100
Other Liabilities [Member]
Other liabilities	150	165
Other Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Other liabilities	150	165
Renewable Energy [Member] | Other Noncurrent Assets [Member]
Other assets	$ 19	$ 21