Segments - Revenue Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Revenue
Revenue	$ 17,560	$ 18,028	$ 53,253	$ 55,370	$ 77,000
Business Segments
Revenue
Revenue	19,193	19,427	57,870	58,956
Other
Revenue
Other - divested businesses	4	83	36	863
Other revenue	46	59	127	190
Internal transactions
Revenue
Revenue	$ (1,683)	$ (1,541)	$ (4,780)	$ (4,638)