Supplemental Financial Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Variable Interest Entities
Assets	$ 51,425		$ 51,425		$ 49,519
Revenues	6,116	$ 6,698	19,060	$ 20,941
Operating income	959	1,036	3,162	4,286
Lease Income
Lease income	$ 32	$ 42	$ 85	$ 120
ConsolidatedVIE [Member]
Variable Interest Entities
Ownership of consolidated VIE	51.00%		51.00%
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities
Assets	$ 1,310		$ 1,310		141
Liabilities	(232)		(232)		$ (22)
Revenues	50		606
Operating income	$ 6		$ 504