Leases (Lease and Other Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Operating Lease, Cost	$ 37	$ 272	$ 100	$ 378
Short-term Lease, Cost	10	11	34	38
Sublease Income	(1)	(1)	(3)	(8)
Lease, Cost	46	282	131	408
Operating Lease, Payments	53	47	141	137
Right-of-use assets obtained in exchange for new operating lease liabilities	32	$ 17	192	$ 372
Other Noncurrent Assets [Member]
Operating Lease, Right-of-Use Asset	685		685		$ 646
Other Current Liabilities [Member]
Operating Lease, Liability, Current	141		141		110
Other Noncurrent Liabilities [Member]
Operating Lease, Liability, Noncurrent	$ 806		$ 806		$ 847