Debt - Debt Covenants (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Coverage ratio of debt-to-EBITDA, maximum	5.00
Ratio of debt-to-EBITDA during acquisition period, maximum	5.50
Threshold for acquisition period qualification	$ 150
Outstanding letters of credit	98	$ 129
Credit agreements and commercial paper program
Debt Instrument [Line Items]
Total borrowings	32,500	29,300	$ 13,300
Total repayments	$ 33,200	$ 29,000	$ 12,900
Letters of credit | Maximum
Debt Instrument [Line Items]
Periods for which letters of credit are issued	70 days