Reclassifications from Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning	$ 2,937	$ 2,193	$ 2,362	$ 1,979
Net current-period other comprehensive income	4	0	4	0
Balance ending	3,082	2,250	3,082	2,250
Pension and Other Postretirement
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning			(22)
Other comprehensive income before reclassifications			0
Amounts reclassified from other comprehensive income			4
Net current-period other comprehensive income			4
Balance ending	(18)		(18)
Foreign Currency
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning			(14)
Other comprehensive income before reclassifications			0
Amounts reclassified from other comprehensive income			0
Net current-period other comprehensive income			0
Balance ending	(14)		(14)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning	(36)	(44)	(36)	(44)
Other comprehensive income before reclassifications			0
Amounts reclassified from other comprehensive income			4
Net current-period other comprehensive income	4		4
Balance ending	$ (32)	$ (44)	$ (32)	$ (44)

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, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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