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, 2021		Jun. 30, 2021	Sep. 30, 2020		Sep. 30, 2021		Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning	$ (18)		$ 586	$ 823		$ 497		$ 3,246
Other comprehensive income	1	[1]	3	1	[1]	4	[1]	1	[1]
Balance ending	(286)		(18)	384		(286)		384
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning	(35)		(38)	(33)		(38)		(33)
Other comprehensive income before reclassifications						0
Amounts reclassified from other comprehensive income						4
Other comprehensive income	1		3	1		4
Balance ending	(34)		$ (35)	$ (32)		(34)		$ (32)
Pension and Other Postretirement
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning						(24)
Other comprehensive income before reclassifications						0
Amounts reclassified from other comprehensive income						4
Other comprehensive income						4
Balance ending	(20)					(20)
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
Other comprehensive income						0
Balance ending	$ (14)					$ (14)

[1] Tax benefits for the three months ended September 30, 2021 and 2020 were immaterial. Net of $1 million in taxes for the nine months ended September 30, 2021 and 2020, respectively.