Segment Reporting Segment Asset Reconciliation (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Segment Reporting [Abstract]
Segment Assets	$ 36,240	$ 36,850	$ 36,965
Corporate Assets	4,882	5,799	4,725
Total Assets	$ 41,122	$ 42,649	$ 41,690

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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+ Details