Organization and Basis of Presentation (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Noncontrolling Interest [Line Items]
Other current liabilities	$ 2,239	$ 2,239		$ 2,936
Charges related to reduction in physical workspace	9	184
Impairment of assets and other charges
Noncontrolling Interest [Line Items]
Charges related to reduction in physical workspace	8	139
Operation, maintenance and other
Noncontrolling Interest [Line Items]
Charges related to reduction in physical workspace	1	28
Depreciation and amortization
Noncontrolling Interest [Line Items]
Charges related to reduction in physical workspace		17
Forecast
Noncontrolling Interest [Line Items]
Charges related to reduction in physical workspace			$ 200
ACP
Noncontrolling Interest [Line Items]
Other current liabilities	$ 36	$ 36		$ 936