Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of year	$ 1,916
Balance at end of period	1,827
Other comprehensive income (loss) attributable to noncontrolling interests	6	$ 8
Foreign currency translation adjustments and other
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of year	(395)	(263)
Other comprehensive income (loss) before reclassifications	27	19
Reclassification from other comprehensive income (loss)	0	0
Other comprehensive income (loss)	(368)	(244)
Income tax provision (benefit)	2	0
Balance at end of period	(366)	(244)
Pensions and other postretirement benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of year	(297)	(275)
Other comprehensive income (loss) before reclassifications	0	0
Reclassification from other comprehensive income (loss)	1	4
Other comprehensive income (loss)	(296)	(271)
Income tax provision (benefit)	0	(1)
Balance at end of period	(296)	(272)
Cash flow hedge instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of year	0	0
Other comprehensive income (loss) before reclassifications	4	0
Reclassification from other comprehensive income (loss)	0	0
Other comprehensive income (loss)	4	0
Income tax provision (benefit)	0	0
Balance at end of period	$ 4	$ 0