Segment Reporting Segment Asset Reconciliation (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Assets		$ 39,108	$ 38,879	$ 40,041
Corporate Assets		3,870	3,518	3,991
Total assets of discontinued operations	[1]	0	0	66,070
Total Assets		$ 42,978	$ 42,397	$ 110,102

[1] See Note 3 - Divestitures and Other Transactions for additional information on discontinued operations.