Reclassifications from Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning	$ 823	$ 3,082	$ 2,937	$ 3,246
Net current-period other comprehensive income	1	1	4
Balance ending	384	3,135	3,082	384
Pension and Other Postretirement
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning				(19)
Other comprehensive income before reclassifications				0
Amounts reclassified from other comprehensive income				1
Net current-period other comprehensive income				1
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	(33)	(32)	(36)	(33)
Other comprehensive income before reclassifications				0
Amounts reclassified from other comprehensive income				1
Net current-period other comprehensive income	1	1	4	1
Balance ending	$ (32)	$ (31)	$ (32)	$ (32)