Equity, Income Tax Effects on Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Before-Tax Amount
Other comprehensive income (loss) before income tax expense (benefit)	$ 83	$ 107	$ (468)
Tax Expense (Benefit)
Income tax expense (benefit) related to items of other comprehensive income (loss)	(16)	(48)	10
Net Amount
Other comprehensive income (loss)	99	155	(478)
Foreign Currency Translation Adjustment [Member]
Before-Tax Amount
Other comprehensive income (loss), before reclassifications, before tax	161	349	(517)
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	161	349	(517)
Net Gain (Loss) on Pension and Other Postretirement Benefits [Member]
Before-Tax Amount
Other comprehensive income (loss) before income tax expense (benefit)	(80)	(234)	49
Tax Expense (Benefit)
Income tax expense (benefit) related to items of other comprehensive income (loss)	(15)	(47)	10
Net Amount
Other comprehensive income (loss)	(65)	(187)	39
Net Actuarial Gain (Loss) [Member]
Before-Tax Amount
Other comprehensive income (loss), before reclassifications, before tax	(128)	(245)	1
Reclassification from accumulated other comprehensive loss, current period, before tax	74	38	63
Tax Expense (Benefit)
Other comprehensive income (loss), before reclassifications, tax expense (benefit)	(26)	(54)	0
Reclassification from accumulated other comprehensive loss, current period, tax expense (benefit)	17	9	14
Net Amount
Other comprehensive income (loss), before reclassifications, net of tax	(102)	(191)	1
Reclassification from accumulated other comprehensive loss, current period, net of tax	57	29	49
Prior Service Cost (Credit) [Member]
Before-Tax Amount
Other comprehensive income (loss), before reclassifications, before tax	(5)	(3)	7
Reclassification from accumulated other comprehensive loss, current period, before tax	(26)	(28)	(29)
Tax Expense (Benefit)
Other comprehensive income (loss), before reclassifications, tax expense (benefit)	(1)	(1)	1
Reclassification from accumulated other comprehensive loss, current period, tax expense (benefit)	(6)	(6)	(7)
Net Amount
Other comprehensive income (loss), before reclassifications, net of tax	(4)	(2)	6
Reclassification from accumulated other comprehensive loss, current period, net of tax	(20)	(22)	(22)
Miscellaneous Loss [Member]
Before-Tax Amount
Other comprehensive income (loss), before reclassifications, before tax		0
Tax Expense (Benefit)
Other comprehensive income (loss), before reclassifications, tax expense (benefit)		4
Net Amount
Other comprehensive income (loss), before reclassifications, net of tax		(4)
Curtailment and Settlement Loss [Member]
Before-Tax Amount
Reclassification from accumulated other comprehensive loss, current period, before tax	5	4	7
Tax Expense (Benefit)
Reclassification from accumulated other comprehensive loss, current period, tax expense (benefit)	1	1	2
Net Amount
Reclassification from accumulated other comprehensive loss, current period, net of tax	4	3	$ 5
Net Gain (Loss) from Derivative Instruments Designated and Qualifying as Cash Flow Hedges [Member]
Before-Tax Amount
Other comprehensive income (loss), before reclassifications, before tax	36	(6)
Reclassification from accumulated other comprehensive loss, current period, before tax	(34)	(2)
Other comprehensive income (loss) before income tax expense (benefit)	2	(8)
Tax Expense (Benefit)
Other comprehensive income (loss), before reclassifications, tax expense (benefit)	3	(1)
Reclassification from accumulated other comprehensive loss, current period, tax expense (benefit)	(4)	0
Income tax expense (benefit) related to items of other comprehensive income (loss)	(1)	(1)
Net Amount
Other comprehensive income (loss), before reclassifications, net of tax	33	(5)
Reclassification from accumulated other comprehensive loss, current period, net of tax	(30)	(2)
Other comprehensive income (loss)	$ 3	$ (7)