Leases Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Payments for Operating Activities [Abstract]
Operating Lease, Payments	$ 398	$ 379
Finance Lease, Interest Payment on Liability	22	26
Finance Lease, Principal Payments	85	85
Right-of-use assets acquired under operating leases	915	230
Right-of-use assets acquired under finance leases	$ 0	$ 1