Equity (AOCI) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI roll forward
Balance	$ 13,114	$ 12,711	$ 15,805
Other comprehensive income (loss) attributable to controlling interest	(21)	11	(7)
Balance	11,867	13,114	12,711
Defined benefit pension plans
AOCI roll forward
Balance	(279)	(290)
Other comprehensive income (loss) before reclassifications	(25)	6
Reclassifications to net income	4	5
Other comprehensive income (loss) attributable to controlling interest	(21)	11
Effect of adopting accounting standards update	(24)
Balance	$ (324)	$ (279)	$ (290)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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