Equity, Income Tax Effects on Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Before-Tax Amount
Other comprehensive income (loss) before income tax expense (benefit)		$ (468)	$ 449	$ (513)
Tax Expense (Benefit)
Income tax expense (benefit) related to items of other comprehensive income (loss)		10	(21)	(37)
Net Amount
Reclassification from accumulated other comprehensive income (loss), current period, net of tax		32	12	7
Other comprehensive income (loss)		(478)	470	(476)
Foreign Currency Translation Adjustment [Member]
Before-Tax Amount
Other comprehensive income (loss), before reclassifications, before tax		(517)	514	(415)
Tax Expense (Benefit)
Other comprehensive income (loss), before reclassifications, tax expense (benefit)		0	0	0
Net Amount
Other comprehensive income (loss), before reclassifications, net of tax		(517)	514	(415)
Net Actuarial Gain (Loss) [Member]
Before-Tax Amount
Other comprehensive income (loss), before reclassifications, before tax		1	(79)	(110)
Reclassification from accumulated other comprehensive income (loss), current period, before tax	[1]	63	50	48
Tax Expense (Benefit)
Other comprehensive income (loss), before reclassifications, tax expense (benefit)		0	(29)	(34)
Reclassification from accumulated other comprehensive income (loss), current period, tax expense (benefit)		14	18	18
Net Amount
Other comprehensive income (loss), before reclassifications, net of tax		1	(50)	(76)
Reclassification from accumulated other comprehensive income (loss), current period, net of tax		49	32	30
Prior Service (Cost) Credit [Member]
Before-Tax Amount
Other comprehensive income (loss), before reclassifications, before tax		7	(4)
Reclassification from accumulated other comprehensive income (loss), current period, before tax	[1]	(29)	(36)	(36)
Tax Expense (Benefit)
Other comprehensive income (loss), before reclassifications, tax expense (benefit)		1	(1)
Reclassification from accumulated other comprehensive income (loss), current period, tax expense (benefit)		(7)	(13)	(13)
Net Amount
Other comprehensive income (loss), before reclassifications, net of tax		6	(3)
Reclassification from accumulated other comprehensive income (loss), current period, net of tax		(22)	(23)	(23)
Miscellaneous Gain (Loss) [Member]
Before-Tax Amount
Other comprehensive income (loss), before reclassifications, before tax			0	0
Tax Expense (Benefit)
Other comprehensive income (loss), before reclassifications, tax expense (benefit)			3	(8)
Net Amount
Other comprehensive income (loss), before reclassifications, net of tax			(3)	8
Curtailment and Settlement Loss [Member]
Before-Tax Amount
Reclassification from accumulated other comprehensive income (loss), current period, before tax	[1]	7	4	0
Tax Expense (Benefit)
Reclassification from accumulated other comprehensive income (loss), current period, tax expense (benefit)		2	1
Net Amount
Reclassification from accumulated other comprehensive income (loss), current period, net of tax		5	3
Net Gain (Loss) on Pension and Other Postretirement Benefits [Member]
Before-Tax Amount
Reclassification from accumulated other comprehensive income (loss), current period, before tax		41	18	12
Other comprehensive income (loss) before income tax expense (benefit)		49	(65)	(98)
Tax Expense (Benefit)
Reclassification from accumulated other comprehensive income (loss), current period, tax expense (benefit)		9	6	5
Income tax expense (benefit) related to items of other comprehensive income (loss)		10	(21)	(37)
Net Amount
Other comprehensive income (loss)		$ 39	$ (44)	$ (61)

[1] These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost (credit), as discussed in Note 13.