Long-Term Debt and Short-Term Borrowings - Long-Term Debt (Details) € in Millions, $ in Millions	Dec. 31, 2018 EUR (€)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Oct. 31, 2017 USD ($)	Sep. 30, 2016 USD ($)	May 31, 2016 EUR (€)	Jun. 30, 2014 USD ($)	Dec. 31, 2004 USD ($)
Long-Term Debt
Total long-term debt		$ 14,156		$ 13,198
Long-term debt (excluding current portion)		13,411		12,096
Floating rate Euro medium term note due 2018
Long-Term Debt
Total long-term debt				600
Floating rate medium term note due 2018
Long-Term Debt
Total long-term debt				448
Floating rate medium term note due 2019
Long-Term Debt
Principal amount		$ 600
Interest rate - effective	1.74%	1.74%
Total long-term debt		$ 596		596
Fixed rate medium term note due 2019
Long-Term Debt
Principal amount		$ 25						$ 625
Interest rate - effective	1.74%	1.74%
Total long-term debt		$ 25		25
Floating rate Euro medium term note due 2020
Long-Term Debt
Principal amount | €	€ 650
Total long-term debt		743		779
Floating rate medium term note due 2020
Long-Term Debt
Principal amount		$ 300
Interest rate - effective	2.61%	2.61%
Total long-term debt		$ 294		296
Floating rate medium term note due 2020
Long-Term Debt
Principal amount		$ 200
Interest rate - effective	2.69%	2.69%
Total long-term debt		$ 197		198
Floating rate Eurobond due 2021
Long-Term Debt
Principal amount | €	€ 300
Total long-term debt		$ 357		378
Fixed rate Eurobond due 2021
Long-Term Debt
Principal amount | €	€ 300
Interest rate - effective	1.97%	1.97%
Total long-term debt		$ 341		358
Fixed rate medium term note due 2021
Long-Term Debt
Principal amount		$ 600
Interest rate - effective	1.63%	1.63%
Total long-term debt		$ 599		598
Fixed rate medium term note due 2021
Long-Term Debt
Principal amount		$ 200
Interest rate - effective	3.07%	3.07%
Total long-term debt		$ 199
Floating rate medium term notes due 2021
Long-Term Debt
Principal amount		$ 200
Interest rate - effective	3.07%	3.07%
Total long-term debt		$ 201
Fixed rate Euro medium term note due 2022
Long-Term Debt
Principal amount | €	€ 500
Interest rate - effective	0.45%	0.45%
Total long-term debt		$ 570		597
Fixed rate medium term note due 2022
Long-Term Debt
Principal amount		$ 600
Interest rate - effective	2.17%	2.17%
Total long-term debt		$ 596		595
Fixed rate Euro medium term note due 2023
Long-Term Debt
Principal amount | €	€ 600
Interest rate - effective	1.14%	1.14%
Total long-term debt		$ 680		712
Fixed rate medium term notes due 2023
Long-Term Debt
Principal amount		$ 650			$ 650
Interest rate - effective	2.26%	2.26%			2.25%
Total long-term debt		$ 648		647
Floating rate medium term notes due 2024
Long-Term Debt
Principal amount		$ 300	$ 300
Interest rate - effective	2.91%	2.91%
Total long-term debt		$ 299
Fixed rate medium term notes due 2024
Long-Term Debt
Principal amount		$ 300	$ 300
Interest rate - effective	3.30%	3.30%	3.25%
Total long-term debt		$ 298
Fixed rate medium term note due 2025
Long-Term Debt
Principal amount		$ 550
Interest rate - effective	3.04%	3.04%
Total long-term debt		$ 547		546
Fixed rate Euro medium term note due 2026
Long-Term Debt
Principal amount | €	€ 750
Interest rate - effective	1.65%	1.65%
Total long-term debt		$ 844		885
Fixed rate medium term notes due 2026
Long-Term Debt
Principal amount		$ 650
Interest rate - effective	2.37%	2.37%
Total long-term debt		$ 642		641
Fixed rate medium term notes due 2027
Long-Term Debt
Principal amount		$ 850			$ 850
Interest rate - effective	2.95%	2.95%			2.875%
Total long-term debt		$ 841		839
Fixed rate 30-year debenture due 2028
Long-Term Debt
Principal amount		$ 220
Interest rate - effective	6.01%	6.01%
Total long-term debt		$ 226		227
Fixed rate medium term notes due 2028
Long-Term Debt
Principal amount		$ 600	$ 600
Interest rate - effective	3.62%	3.62%	3.625%
Total long-term debt		$ 597
Fixed rate Euro medium term note due 2030
Long-Term Debt
Principal amount | €	€ 500
Interest rate - effective	1.90%	1.90%
Total long-term debt		$ 562		589
Fixed rate Euro medium term notes due 2031
Long-Term Debt
Principal amount | €	€ 500
Interest rate - effective	1.54%	1.54%
Total long-term debt		$ 567		595
Fixed rate 30-year bond due 2037
Long-Term Debt
Principal amount		$ 555
Interest rate - effective	5.73%	5.73%
Total long-term debt		$ 551		550
Floating rate note due 2041
Long-Term Debt
Principal amount		$ 96
Interest rate - effective	2.45%	2.45%
Total long-term debt		$ 95		95
Fixed rate medium term note due 2044
Long-Term Debt
Principal amount		$ 325
Interest rate - effective	4.05%	4.05%
Total long-term debt		$ 314		313
Floating rate note due 2044
Long-Term Debt
Principal amount		$ 55							$ 60
Interest rate - effective	2.43%	2.43%
Total long-term debt		$ 53		54
Fixed rate medium term note due 2046
Long-Term Debt
Principal amount		$ 500
Interest rate - effective	3.37%	3.37%
Total long-term debt		$ 474		473
Fixed rate medium term note due 2047
Long-Term Debt
Principal amount		$ 500			$ 500
Interest rate - effective	3.68%	3.68%			3.625%
Total long-term debt		$ 491		491
Fixed rate medium term note due 2048
Long-Term Debt
Principal amount		$ 650	$ 650
Interest rate - effective	4.07%	4.07%	4.00%
Total long-term debt		$ 637
Various fixed and floating rate of other borrowings due 2019-2040
Long-Term Debt
Interest rate - effective	2.35%	2.35%
Total long-term debt		$ 72		73
May 2016 Euro medium term notes issued
Long-Term Debt
Principal amount | €							€ 1,000
September 2016 medium term notes issued
Long-Term Debt
Principal amount						$ 1,750
Current portion of long-term debt
Long-Term Debt
Interest rate - effective	1.85%	1.85%
Total long-term debt		$ 745		$ 1,102