Leases (Lease and Other Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Lease, Cost	$ 438	$ 198
Short-term Lease, Cost	50	46
Sublease Income	9	16
Lease, Cost	479	228	$ 207
Operating Lease, Payments	207	176
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 384	$ 112
Operating Lease, Weighted Average Remaining Lease Term	7 years	6 years
Operating Lease, Weighted Average Discount Rate, Percent	3.21%	4.09%
Other Noncurrent Assets [Member]
Operating Lease, Right-of-Use Asset	$ 646	$ 575
Other Current Liabilities [Member]
Operating Lease, Liability, Current	110	158
Other Noncurrent Liabilities [Member]
Operating Lease, Liability, Noncurrent	$ 847	$ 482