Revenue Recognition (Allowance for Doubtful Accounts Rollforward) (Details) - Allowance for doubtful accounts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ 108	$ 103	$ 93
Charged to Costs and Expenses	5	9	8
Charged to Revenue	31	25	34
Deductions and other	(32)	(29)	(32)
Ending balance	$ 112	$ 108	$ 103