Commitments and Contingencies (Guarantees - Demerger and Divesture Obligations Narrative) (Details) € in Millions, $ in Millions	9 Months Ended	227 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 EUR (€)
Indemnification Agreements Hoechst [Member]
Loss Contingencies [Line Items]
Number of divestiture agreements	19	19	19
Indemnification amount | €			€ 250
Indemnification ceiling amount | €			€ 750
Indemnification percentage exceeding ceiling amount	33.33%	33.33%	33.33%
Loss contingency accrual, carrying value, payments | $		$ 84
Indemnification percentage, other	33.33%	33.33%	33.33%
Divestiture Agreements [Member]
Loss Contingencies [Line Items]
Term of divestiture obligations	2037
Guarantor obligations, maximum exposure | $	$ 122	$ 122