SCHEDULE I, CONDENSED FINANCIAL INFORMATION OF PARENT - STATEMENT OF COMPREHENSIVE INCOME (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Condensed Statement of Income Captions [Line Items]
Net income	$ 351	$ 1,519	[1]	$ 1,448	[1]
Total other comprehensive income (loss)	142	52		(334)
Pretax amount [Member]
Condensed Statement of Income Captions [Line Items]
Net income	1,533	1,760		1,691
Foreign currency translation adjustments	107	42		(260)
Financial instruments	2	(6)		(80)
Pension and other postretirement benefits	20	(13)		(3)
Total other comprehensive income (loss)	129	23		(343)
Total comprehensive income, after preferred dividends of subsidiaries	1,661	1,782		1,347
Income tax benefit [Member]
Condensed Statement of Income Captions [Line Items]
Net income	(1,276)	(389)		(341)
Foreign currency translation adjustments	0	0		0
Financial instruments	1	11		33
Pension and other postretirement benefits	(8)	4		1
Total other comprehensive income (loss)	(7)	15		34
Total comprehensive income, after preferred dividends of subsidiaries	(1,283)	(374)		(307)
Net-of-tax amount [Member]
Condensed Statement of Income Captions [Line Items]
Net income	257	1,371		1,350
Foreign currency translation adjustments	107	42		(260)
Financial instruments	3	5		(47)
Pension and other postretirement benefits	12	(9)		(2)
Total other comprehensive income (loss)	122	38		(309)
Total comprehensive income, after preferred dividends of subsidiaries	378	1,408		1,040
Parent Company [Member] | Pretax amount [Member]
Condensed Statement of Income Captions [Line Items]
Net income	223	1,189		1,199
Foreign currency translation adjustments	107	42		(260)
Financial instruments	2	(6)		(80)
Pension and other postretirement benefits	20	(13)		(3)
Total other comprehensive income (loss)	129	23		(343)
Total comprehensive income, after preferred dividends of subsidiaries	352	1,212		856
Parent Company [Member] | Income tax benefit [Member]
Condensed Statement of Income Captions [Line Items]
Net income	33	181		150
Foreign currency translation adjustments	0	0		0
Financial instruments	1	11		33
Pension and other postretirement benefits	(8)	4		1
Total other comprehensive income (loss)	(7)	15		34
Total comprehensive income, after preferred dividends of subsidiaries	26	196		184
Parent Company [Member] | Net-of-tax amount [Member]
Condensed Statement of Income Captions [Line Items]
Net income	256	1,370		1,349
Foreign currency translation adjustments	107	42		(260)
Financial instruments	3	5		(47)
Pension and other postretirement benefits	12	(9)		(2)
Total other comprehensive income (loss)	122	38		(309)
Total comprehensive income, after preferred dividends of subsidiaries	$ 378	$ 1,408		$ 1,040

[1] As adjusted for the retrospective adoption of ASU 2016-15 and ASU 2016-18, which we discuss in Note 2.