Segments - Revenue Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenue
Revenue	$ 18,123	$ 19,161	$ 35,694	$ 37,342	$ 77,000
Business Segments
Revenue
Revenue	19,655	20,131	38,677	39,529
Other
Revenue
Other - divested businesses	13	403	32	780
Other revenue	37	57	81	131
Internal transactions
Revenue
Revenue	$ (1,582)	$ (1,430)	$ (3,096)	$ (3,097)