Deferred and current taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Taxes [Abstract]
Income tax receivables	$ 14,122		$ 14,122		$ 16,377
Income tax liabilities	36,841		36,841		$ 15,539
Income taxes	$ 12,169	$ 8,436	$ 45,891	$ 27,422
Effective tax rate in %			31.20%	35.20%
Applicable tax rate			32.00%	32.00%
Tax rate effect of change in recognition of losses and deductible temporary differences			3.44%	2.60%
Tax rate effect of revenues exempt from taxation			0.40%	1.40%
Tax rate effect of foreign tax rates			3.59%
Tax rate effect of tax exempt dividends from subsidiary				1.80%
Tax rate effect from change in tax rate				6.10%

The applicable income tax rate.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2017-01-01
-Paragraph 81
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_c_ii&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ApplicableTaxRate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The tax expense (income) divided by the accounting profit. [Refer: Accounting profit]

+ References

+ Details

Name:	ifrs-full_AverageEffectiveTaxRate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The current amount of current tax assets. [Refer: Current tax assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 54
-Subparagraph n
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_n&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_CurrentTaxAssetsCurrent
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The current amount of current tax liabilities. [Refer: Current tax liabilities]

+ References

+ Details

Name:	ifrs-full_CurrentTaxLiabilitiesCurrent
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate amount included in the determination of profit (loss) for the period in respect of current tax and deferred tax that relate to continuing operations. [Refer: Continuing operations [member]; Current tax expense (income); Deferred tax expense (income)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2017-01-01
-Paragraph 23
-Subparagraph h
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2017-03-01&anchor=para_23_h&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 26
-IssueDate 2017-01-01
-Paragraph 35
-Subparagraph b
-Clause viii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=26&date=2017-03-01&anchor=para_35_b_viii&doctype=Standard
-URIDate 2017-03-09

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2017-01-01
-Paragraph 79
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_79&doctype=Standard
-URIDate 2017-03-09

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2017-01-01
-Paragraph 81
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_c_i&doctype=Standard
-URIDate 2017-03-09

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 82
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_82_d&doctype=Standard
-URIDate 2017-03-09

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2017-01-01
-Paragraph 81
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_c_ii&doctype=Standard
-URIDate 2017-03-09

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2017-01-01
-Paragraph B13
-Subparagraph g
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2017-03-01&anchor=para_B13_g&doctype=Appendix&seq=2
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_IncomeTaxExpenseContinuingOperations
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The tax rate effect on the reconciliation between the average effective tax rate and the applicable tax rate resulting from a change in tax rate. [Refer: Average effective tax rate; Applicable tax rate]

+ References

+ Details

Name:	ifrs-full_TaxRateEffectFromChangeInTaxRate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The tax rate effect on the reconciliation between the average effective tax rate and the applicable tax rate resulting from the application of foreign tax rates. [Refer: Average effective tax rate; Applicable tax rate]

+ References

+ Details

Name:	ifrs-full_TaxRateEffectOfForeignTaxRates
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The tax rate effect on the reconciliation between the average effective tax rate and the applicable tax rate resulting from revenue that is exempt from taxation. [Refer: Average effective tax rate; Applicable tax rate]

+ References

+ Details

Name:	ifrs-full_TaxRateEffectOfRevenuesExemptFromTaxation
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Income Taxes [Abstract]

+ References

No definition available.

+ Details

Name:	oec_IncomeTaxesAbstract
Namespace Prefix:	oec_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax Rate Effect Of Change In Recognition Of Losses And Deductible Temporary Differences

+ References

No definition available.

+ Details

Name:	oec_TaxRateEffectOfChangeInRecognitionOfLossesAndDeductibleTemporaryDifferences
Namespace Prefix:	oec_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax Rate Effect Of Tax Exempt Dividends From Subsidiary

+ References

No definition available.

+ Details

Name:	oec_TaxRateEffectOfTaxExemptDividendsFromSubsidiary
Namespace Prefix:	oec_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration