Segment Reporting Segment Asset Reconciliation (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Segment Reporting [Abstract]
Document Period End Date		Sep. 30, 2019
Segment Assets		$ 39,352	$ 38,632	$ 39,388
Corporate Assets		3,883	4,417	4,020
Total assets of discontinued operations	[1]	0	65,634	66,240
Total Assets		$ 43,235	$ 108,683	$ 109,648

[1] See Note 5 - Divestitures and Other Transactions for additional information on discontinued operations.