Pensions Benefit Plans and Other Postretirement Benefits - Reconciliation of Pension Plan Assets Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
U.S. Pension Plans
Defined Benefit Plan Disclosure
Fair value at beginning of year	$ 1,654	$ 1,909
Net increase (decrease)	(260)	(255)
Fair value at end of year	1,394	1,654
Non-U.S. Pension Plans
Defined Benefit Plan Disclosure
Fair value at beginning of year	1,011	1,012
Net increase (decrease)	(36)	(1)
Fair value at end of year	975	1,011
Other | Non-U.S. Pension Plans
Defined Benefit Plan Disclosure
Fair value at beginning of year	43
Fair value at end of year	27	43
Level 3 | Non-U.S. Pension Plans
Defined Benefit Plan Disclosure
Fair value at beginning of year	10	11
Net increase (decrease)	(10)	(1)
Fair value at end of year		10
Level 3 | Other | Non-U.S. Pension Plans
Defined Benefit Plan Disclosure
Fair value at beginning of year	$ 6
Fair value at end of year		$ 6