Financial Instruments - Derivatives (Details) € in Millions, ₩ in Millions, ¥ in Millions, ¥ in Millions, £ in Millions, kr in Millions, $ in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($) t	Dec. 31, 2018 USD ($) t	Mar. 31, 2019 JPY (¥)	Mar. 31, 2019 KRW (₩)	Mar. 31, 2019 CNY (¥)	Mar. 31, 2019 SEK (kr)	Mar. 31, 2019 EUR (€)	Mar. 31, 2019 MXN ($)	Mar. 31, 2019 GBP (£)	Dec. 31, 2018 JPY (¥)	Dec. 31, 2018 KRW (₩)	Dec. 31, 2018 CNY (¥)	Dec. 31, 2018 SEK (kr)	Dec. 31, 2018 EUR (€)	Dec. 31, 2018 MXN ($)	Dec. 31, 2018 GBP (£)
Commodity contracts | Maturity December 2019
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | t	188	257
Brazil, Brazil Real | Foreign currency | Maturity June 2019
Derivative [Line Items]
Notional amount of currency derivatives	$ 3	$ 5					€ 2							€ 4
China, Yuan Renminbi | Foreign currency | Maturity December 2019
Derivative [Line Items]
Notional amount of currency derivatives	17	0
Euro Member Countries, Euro | Cross Currency Interest Rate Contract [Member] | Maturity September 2020
Derivative [Line Items]
Notional amount of currency derivatives | €							206
Euro Member Countries, Euro | Foreign currency | Maturity June 2019
Derivative [Line Items]
Notional amount of currency derivatives | kr						kr 540							kr 540
Euro Member Countries, Euro | Foreign currency | Maturity December 2019
Derivative [Line Items]
Notional amount of currency derivatives	10	19			¥ 39				£ 10			¥ 0				£ 7
Japan, Yen | Cross Currency Interest Rate Contract [Member] | Maturity February 2023
Derivative [Line Items]
Notional amount of currency derivatives | ¥			¥ 10,978
Japan, Yen | Foreign currency | Maturity December 2019
Derivative [Line Items]
Notional amount of currency derivatives	2	3		₩ 4,243	¥ 66						₩ 5,785	¥ 89
Korea (South), Won | Foreign currency | Maturity December 2019
Derivative [Line Items]
Notional amount of currency derivatives	30	$ 7	¥ 186				5			¥ 266				6
Sweden, Kronor | Foreign currency | Maturity January 2020
Derivative [Line Items]
Notional amount of currency derivatives | €							44							56
United States of America, Dollars | Cross Currency Interest Rate Contract [Member] | Maturity September 2020
Derivative [Line Items]
Notional amount of currency derivatives	250
United States of America, Dollars | Cross Currency Interest Rate Contract [Member] | Maturity February 2023
Derivative [Line Items]
Notional amount of currency derivatives	$ 100
United States of America, Dollars | Foreign currency | Maturity December 2019
Derivative [Line Items]
Notional amount of currency derivatives								$ 445							$ 575
United States of America, Dollars | Foreign currency | Maturity January 2020
Derivative [Line Items]
Notional amount of currency derivatives | €							€ 14							€ 0