Supplemental Balance Sheet Information - Changes in Balances of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ 1,886	$ 1,436	$ 408
Other comprehensive (loss) income, net of tax	(4)	(71)	24
Balance at end of period	1,845	1,886	1,436
Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	27	20	16
Other comprehensive income (loss) before reclassifications, net of tax	(14)	1	(5)
Less: Amounts reclassified from AOCI, net of tax	(3)	(6)	(9)
Other comprehensive (loss) income, net of tax	(11)	7	4
Balance at end of period	16	27	20
Pension and Other Postretirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(246)	(221)	(302)
Other comprehensive income (loss) before reclassifications, net of tax	(65)	(34)	74
Less: Amounts reclassified from AOCI, net of tax	(14)	(9)	(7)
Other comprehensive (loss) income, net of tax	(51)	(25)	81
Balance at end of period	(297)	(246)	(221)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(166)	(113)	(52)
Other comprehensive income (loss) before reclassifications, net of tax	58	(53)	(67)
Less: Amounts reclassified from AOCI, net of tax	0	0	(6)
Other comprehensive (loss) income, net of tax	58	(53)	(61)
Balance at end of period	(108)	(166)	(113)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(385)	(314)	(338)
Other comprehensive income (loss) before reclassifications, net of tax	(21)	(86)	2
Less: Amounts reclassified from AOCI, net of tax	(17)	(15)	(22)
Other comprehensive (loss) income, net of tax	(4)	(71)	24
Balance at end of period	$ (389)	$ (385)	$ (314)