Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss by Component (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jan. 01, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 659	$ 693	$ 745	$ 781	$ 659
Other comprehensive (loss) income before reclassifications		(3)	(14)	(34)	(24)
Amounts reclassified from AOCL		(3)	(4)	(8)	(7)
Income tax		2	4	9	7
Reclassification of stranded tax effects	7				7
Net current period other comprehensive (loss) income		(4)	(14)	(33)	(17)
Balance		695	668	695	668
Pension and OPEB liability adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	9	4	15	8	9
Other comprehensive (loss) income before reclassifications		0	0	0	0
Amounts reclassified from AOCL		(3)	(4)	(8)	(7)
Income tax		1	1	2	2
Reclassification of stranded tax effects					8
Net current period other comprehensive (loss) income		(2)	(3)	(6)	3
Balance		2	12	2	12
Available-for-sale securities and interest rate swaps
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(7)	(49)	(16)	(26)	(7)
Other comprehensive (loss) income before reclassifications		(3)	(15)	(32)	(25)
Amounts reclassified from AOCL		0	0	0	0
Income tax		1	3	7	5
Reclassification of stranded tax effects					(1)
Net current period other comprehensive (loss) income		(2)	(12)	(25)	(21)
Balance		(51)	(28)	(51)	(28)
Foreign currency items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(32)	(36)	(32)	(34)	(32)
Other comprehensive (loss) income before reclassifications		0	1	(2)	1
Amounts reclassified from AOCL		0	0	0	0
Income tax		0	0	0	0
Reclassification of stranded tax effects					0
Net current period other comprehensive (loss) income		0	1	(2)	1
Balance		(36)	(31)	(36)	(31)
Accumulated Other Comprehensive Loss, net of tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ (30)	(81)	(33)	(52)	(30)
Balance		$ (85)	$ (47)	$ (85)	$ (47)