Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Tax on foreign currency translation	$ 39	$ (2)	$ (52)
Tax on foreign currency translation reclassification adjustment recognized in income	0	0	0
Defined benefit plans:
Tax on amortization of prior service cost and unrecognized gains and losses included in total benefit cost	40	33	34
Tax on increase in net actuarial losses	(37)	(53)	(19)
Tax on immediate recognition of prior service cost and unrecognized gains and losses due to curtailments, settlements, and divestitures	14	0	67
Tax on prior service cost from plan amendments	(2)	0	0
Tax on deferred derivative gains (losses)	(8)	4	3
Tax on deferred derivative gains (losses) reclassification adjustment recognized in income	1	(1)	(3)
Tax on unrealized investment gains	0	0	(2)
Tax on unrealized investment gains reclassification adjustment recognized in income	0	0	2
Tax on deconsolidation of Venezuelan subsidiary	$ 0	$ 0	$ 0