Summary of Accounting Policies (Pension and Other Postretirement Obligations) (Details)	Dec. 31, 2020
Accounting Policies [Abstract]
Number of Aa-grade non-callable bonds	300

Number of Aa-grade non-callable bonds from which market data is used to develop a yield curve to use as a basis in the US for the rate used to discount pension and postretirement benefit plan liabilities.

No definition available.

Name:	ce_DefinedBenefitPlanAssumptionNumberOfAaGradeNonCallableBonds
Namespace Prefix:	ce_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant