Reclassifications out of Accumulated Other Comprehensive Loss - Changes in AOCL (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 4,507
Balance at end of period	4,603	$ 4,507
Foreign Currency Translation Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(1,155)	(946)	$ (894)
Other comprehensive income (loss) before reclassifications	240	(209)	(251)
Amounts reclassified from accumulated other comprehensive loss	0	0	16
Purchase of subsidiary shares from minority interest			(3)
Deconsolidation of Venezuelan subsidiary			186
Balance at end of period	(915)	(1,155)	(946)
Unrecognized Net Actuarial Losses and Prior Service Costs
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(3,053)	(3,071)	(3,285)
Other comprehensive income (loss) before reclassifications	(103)	(62)	(68)
Amounts reclassified from accumulated other comprehensive loss	104	80	325
Purchase of subsidiary shares from minority interest			(105)
Deconsolidation of Venezuelan subsidiary			62
Balance at end of period	(3,052)	(3,053)	(3,071)
Deferred Derivative Gains (Losses)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	10	7	12
Other comprehensive income (loss) before reclassifications	(20)	8	15
Amounts reclassified from accumulated other comprehensive loss	1	(5)	(21)
Purchase of subsidiary shares from minority interest			1
Deconsolidation of Venezuelan subsidiary			0
Balance at end of period	(9)	10	7
Unrealized Investment Gains
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	0	0	36
Other comprehensive income (loss) before reclassifications	0	0	(4)
Amounts reclassified from accumulated other comprehensive loss	0	0	(32)
Purchase of subsidiary shares from minority interest			0
Deconsolidation of Venezuelan subsidiary			0
Balance at end of period	0	0	0
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(4,198)	(4,010)	(4,131)
Other comprehensive income (loss) before reclassifications	117	(263)	(308)
Amounts reclassified from accumulated other comprehensive loss	105	75	288
Purchase of subsidiary shares from minority interest			(107)
Deconsolidation of Venezuelan subsidiary			248
Balance at end of period	$ (3,976)	$ (4,198)	$ (4,010)