Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$ 346	$ 398	$ 379
Operating cash flows for finance leases	19	22	26
Financing cash flows for finance leases	83	85	85
Right-of-use assets obtained in exchange for lease obligations:
Right-of-use assets acquired under operating leases	327	915	230
Right-of-use assets acquired under finance leases	$ 0	$ 0	$ 1