Leases Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating Lease, Cost	$ 315	$ 275
Short-term Lease, Cost	101	99
Lease, Cost	416	374
Operating Lease, Payments	302	209
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 314	$ 302
Operating Lease, Weighted Average Remaining Lease Term	7 years	7 years
Operating Lease, Weighted Average Discount Rate, Percent	4.20%	4.60%