Related parties - Narrative (Details)	Jun. 30, 2018 joint_venture
Related Party [Abstract]
Number of joint ventures accounted for using the equity method	1

Number Of Joint Ventures, Related Party Transactions

No definition available.

Name:	oec_NumberOfJointVenturesRelatedPartyTransactions
Namespace Prefix:	oec_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant