Long-Term Debt and Short-Term Borrowings - Long-Term Debt (Details) € in Millions, $ in Millions	Dec. 31, 2017 EUR (€)	Dec. 31, 2017 USD ($)	Oct. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	May 31, 2016 EUR (€)	Aug. 31, 2015 USD ($)	May 31, 2015 EUR (€)	Nov. 30, 2014 EUR (€)	Jun. 30, 2014 USD ($)	Dec. 31, 2004 USD ($)
Long-Term Debt
Total long-term debt		$ 13,198.0		$ 11,478.0
Long-term debt (excluding current portion)		12,096.0		10,678.0
Medium-term note (repaid in 2017)
Long-Term Debt
Total long-term debt				649.0
Floating rate Euro medium term note due 2018
Long-Term Debt
Principal amount | €	€ 500.0
Total long-term debt		600.0		523.0
Floating rate medium term note due 2018
Long-Term Debt
Principal amount		$ 450.0
Interest rate - effective	1.50%	1.50%
Total long-term debt		$ 448.0		448.0
Floating rate medium term note due 2019
Long-Term Debt
Principal amount		$ 600.0
Interest rate - effective	1.63%	1.63%
Total long-term debt		$ 596.0		598.0
Fixed rate medium term note due 2019
Long-Term Debt
Principal amount		$ 25.0								$ 625.0
Interest rate - effective	1.74%	1.74%
Total long-term debt		$ 25.0		25.0
Floating rate Euro medium term note due 2020
Long-Term Debt
Principal amount | €	€ 650.0
Total long-term debt		779.0		680.0
Floating rate medium term note due 2020
Long-Term Debt
Principal amount		$ 300.0
Interest rate - effective	1.58%	1.58%
Total long-term debt		$ 296.0		297.0
Fixed rate medium term note due 2020
Long-Term Debt
Principal amount		$ 200.0
Interest rate - effective	1.49%	1.49%
Total long-term debt		$ 198.0		199.0
Floating rate Eurobond due 2021
Long-Term Debt
Principal amount | €	€ 300.0
Total long-term debt		$ 378.0		336.0
Fixed rate Eurobond due 2021
Long-Term Debt
Principal amount | €	€ 300.0
Interest rate - effective	1.97%	1.97%
Total long-term debt		$ 358.0		312.0
Fixed rate medium term notes due 2021
Long-Term Debt
Principal amount		$ 600.0
Interest rate - effective	1.63%	1.63%
Total long-term debt		$ 598.0		598.0
Fixed rate Euro medium term notes due 2022
Long-Term Debt
Principal amount | €	€ 500.0
Interest rate - effective	0.45%	0.45%
Total long-term debt		$ 597.0		520.0
Fixed rate medium term note due 2022
Long-Term Debt
Principal amount		$ 600.0
Interest rate - effective	2.17%	2.17%
Total long-term debt		$ 595.0		593.0
Fixed rate Euro medium term note due 2023
Long-Term Debt
Principal amount | €	€ 600.0
Interest rate - effective	1.14%	1.14%
Total long-term debt		$ 712.0		619.0
Fixed rate medium term notes due 2023
Long-Term Debt
Principal amount		$ 650.0	$ 650.0
Interest rate - effective	2.26%	2.26%	2.25%
Total long-term debt		$ 647.0
Fixed rate medium term note due 2025
Long-Term Debt
Principal amount		$ 550.0
Interest rate - effective	3.04%	3.04%
Total long-term debt		$ 546.0		546.0
Fixed rate Euro Medium term note due 2026
Long-Term Debt
Principal amount | €	€ 750.0
Interest rate - effective	1.71%	1.71%
Total long-term debt		$ 885.0		770.0
Fixed rate medium term notes due 2026
Long-Term Debt
Principal amount		$ 650.0
Interest rate - effective	2.25%	2.25%
Total long-term debt		$ 641.0		640.0
Fixed rate medium term notes due 2027
Long-Term Debt
Principal amount		$ 850.0	$ 850.0
Interest rate - effective	2.95%	2.95%	2.875%
Total long-term debt		$ 839.0
Fixed rate 30-year debenture due 2028
Long-Term Debt
Principal amount		$ 220.0
Interest rate - effective	6.01%	6.01%
Total long-term debt		$ 227.0		342.0
Fixed rate Euro medium term note due 2030
Long-Term Debt
Principal amount | €	€ 500.0
Interest rate - effective	1.90%	1.90%
Total long-term debt		$ 589.0		512.0
Fixed rate Euro medium term notes due 2031
Long-Term Debt
Principal amount | €	€ 500.0
Interest rate - effective	1.54%	1.54%
Total long-term debt		$ 595.0		518.0
Fixed rate 30-year bond due 2037
Long-Term Debt
Principal amount		$ 555.0
Interest rate - effective	5.73%	5.73%
Total long-term debt		$ 550.0		743.0
Floating rate note due 2041
Long-Term Debt
Principal amount		$ 96.0
Interest rate - effective	1.29%	1.29%
Total long-term debt		$ 95.0		96.0
Fixed rate medium term note due 2044
Long-Term Debt
Principal amount		$ 325.0
Interest rate - effective	4.05%	4.05%
Total long-term debt		$ 313.0		313.0
Floating rate note due 2044
Long-Term Debt
Principal amount		$ 55.0									$ 60.0
Interest rate - effective	1.21%	1.21%
Total long-term debt		$ 54.0		54.0
Fixed rate medium term notes due 2046
Long-Term Debt
Principal amount		$ 500.0
Interest rate - effective	3.13%	3.13%
Total long-term debt		$ 473.0		473.0
Fixed rate medium term notes due 2047
Long-Term Debt
Principal amount		$ 500.0	$ 500.0
Interest rate - effective	3.68%	3.68%	3.625%
Total long-term debt		$ 491.0
Various fixed and floating rate Other borrowings due 2018-2040
Long-Term Debt
Interest rate - effective	1.26%	1.26%
Total long-term debt		$ 73.0		74.0
May 2016 Euro medium term notes issued
Long-Term Debt
Principal amount | €						€ 1,000.0
September 2016 medium term notes issued
Long-Term Debt
Principal amount					$ 1,750.0
May 2015 Euro medium term notes issued
Long-Term Debt
Principal amount | €								€ 1,750.0
August 2015 medium term notes issued
Long-Term Debt
Principal amount							$ 1,500.0
June 2014 medium term notes issued
Long-Term Debt
Principal amount										$ 950.0
November 2014 Euro medium term notes issued
Long-Term Debt
Principal amount | €									€ 1,250.0
Current portion of long-term debt
Long-Term Debt
Interest rate - effective	0.67%	0.67%
Total long-term debt		$ 1,102.0		$ 800.0