Leases (Lease and Other Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Operating Lease, Cost	$ 34	$ 59	$ 63	$ 106
Short-term Lease, Cost	12	14	24	27
Sublease Income	(1)	(4)	(2)	(7)
Lease, Cost	45	69	85	126
Operating Lease, Payments	36	46	88	90
Right-of-use assets obtained in exchange for new operating lease liabilities	145	$ 33	160	$ 356
Other Noncurrent Assets [Member]
Operating Lease, Right-of-Use Asset	683		683		$ 646
Other Current Liabilities [Member]
Operating Lease, Liability, Current	144		144		110
Other Noncurrent Liabilities [Member]
Operating Lease, Liability, Noncurrent	$ 833		$ 833		$ 847