Supplementary Financial Information - Statements of (Loss) Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Restricted Cash and Cash Equivalents Items [Line Items]
Selling, administrative and general expenses	$ 459	$ 434	$ 914	$ 882
Total Costs and Expenses	1,752	1,694	3,509	3,351
COVID-19 Pandemic, Aid And Economic Stimulus Savings
Restricted Cash and Cash Equivalents Items [Line Items]
Cost of services, maintenance and rentals	0	6	0	13
Selling, administrative and general expenses	0	4	0	7
Total Costs and Expenses	$ 0	$ 10	$ 0	$ 20