Leases Other supplemental information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019
Leases [Abstract]
Operating cash flows from operating leases	$ 299		$ 316
Operating cash flows from finance leases	32		51
Financing cash flows from finance leases	21		24
Right-of-Use Assets Obtained in Exchange for Operating Lease Liability	447	[1]	1,362
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 39		$ 74
Operating Lease, Weighted Average Remaining Lease Term	8 years 7 months 6 days		9 years 6 months
Finance Lease, Weighted Average Remaining Lease Term	6 years 4 months 24 days		5 years 4 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent	4.10%		4.40%

[1] rimarily consists of operating lease right-of-use assets exchanged for lease obligations upon implementation of the new lease accounting standard on January 1, 2019.