Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss by Component (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jan. 01, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 659	$ 668	$ 602	$ 659	$ 689
Other comprehensive income (loss) before reclassifications		(13)	4	(37)	(3)
Amounts reclassified from AOCL		(3)	(3)	(10)	(10)
Income tax		3	0	10	2
Reclassification of stranded tax effects	7			7
Net current period other comprehensive (loss) income		(13)	1	(30)	(11)
Balance		743	684	743	684
Pension and OPEB liability adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	9	12	3	9	8
Other comprehensive income (loss) before reclassifications		0	0	0	0
Amounts reclassified from AOCL		(3)	(3)	(10)	(10)
Income tax		1	0	3	2
Reclassification of stranded tax effects				8
Net current period other comprehensive (loss) income		(2)	(3)	1	(8)
Balance		10	0	10	0
Available-for-sale securities and interest rate swaps
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(7)	(28)	(2)	(7)	0
Other comprehensive income (loss) before reclassifications		(7)	4	(32)	2
Amounts reclassified from AOCL		0	0	0	0
Income tax		2	0	7	0
Reclassification of stranded tax effects				(1)
Net current period other comprehensive (loss) income		(5)	4	(26)	2
Balance		(33)	2	(33)	2
Foreign currency items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(32)	(31)	(28)	(32)	(23)
Other comprehensive income (loss) before reclassifications		(6)	0	(5)	(5)
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		(6)	0	(5)	(5)
Balance		(37)	(28)	(37)	(28)
Accumulated Other Comprehensive Loss, net of tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ (30)	(47)	(27)	(30)	(15)
Balance		$ (60)	$ (26)	$ (60)	$ (26)