The average rate of a hedging instrument. [Refer: Hedging instruments [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2018-01-01
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph 23B
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-01&anchor=para_23B_b&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_AverageRateOfHedgingInstrument
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of outstanding funds that the entity is obligated to repay.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_55&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

The amount of equity attributable to the owners of the parent. This specifically excludes non-controlling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 54
-Subparagraph r
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_r&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

The nominal or face amount of a financial instrument, used to calculate payments made on that instrument.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 112
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_NotionalAmount
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow for repayments of non-current borrowings. [Refer: Borrowings]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2017-01-01
-Paragraph 17
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=para_17&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_RepaymentsOfNoncurrentBorrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of risk exposure associated with financial instruments with a shared characteristic that identifies a concentration of risks. [Refer: Financial instruments, class [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph B8
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-01&anchor=para_B8_c&doctype=Appendix&seq=2
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_RiskExposureAssociatedWithInstrumentsSharingCharacteristic
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

+ Details

Name:	invest_InvestmentLineItems
Namespace Prefix:	invest_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Borrowings, Minimum Reference Rate

+ References

No definition available.

+ Details

Name:	oec_BorrowingsMinimumReferenceRate
Namespace Prefix:	oec_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Borrowings, Variable Rate, Floor

+ References

No definition available.

+ Details

Name:	oec_BorrowingsVariableRateFloor
Namespace Prefix:	oec_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Percent

+ References

No definition available.

+ Details

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

- Details

Name:	ifrs-full_ComponentsOfEquityAxis=ifrs-full_HedgesOfNetInvestmentInForeignOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_InterestRateRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_CurrencyRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_HedgingInstrumentsAxis=oec_CrossCurrencySwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=oec_CreditFacilityTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=oec_EURDenominatedCreditFacilityTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TypesOfInterestRatesAxis=ifrs-full_FixedInterestRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_HedgingInstrumentsAxis=oec_EuroInterestRateCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=oec_USDenominatedCreditFacilityTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_HedgingInstrumentsAxis=oec_UnitedStatesDollarInterestRateCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Other notes - Financial risk management, market risk, narrative (Details)									12 Months Ended
	Jan. 23, 2017 EUR (€)	Jan. 23, 2017 USD ($)	Jul. 15, 2016 EUR (€)	Jul. 15, 2016 USD ($)	Jan. 29, 2016 EUR (€)	Jan. 29, 2016 USD ($)	Dec. 30, 2015 EUR (€)	Dec. 30, 2015 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2016 EUR (€)	Dec. 31, 2015 EUR (€)	Nov. 07, 2017	Nov. 06, 2017	May 05, 2017	May 04, 2017	Sep. 30, 2016	Sep. 29, 2016	Jan. 31, 2016 USD ($)	Jan. 01, 2015 USD ($)	Dec. 31, 2014 EUR (€)	Nov. 28, 2014 EUR (€)	Nov. 28, 2014 USD ($)	Jul. 25, 2014 EUR (€)	Jul. 25, 2014 USD ($)
Investment [Line Items]
Unrealized foreign exchange loss									€ (83,262,000)	€ (52,882,000)	€ (49,686,000)									€ (55,265,000)
Repayments of non-current borrowings									26,572,000	47,357,000	56,825,000
Borrowings									558,569,000	618,059,000
Hedges of net investment in foreign operations
Investment [Line Items]
Unrealized foreign exchange loss									1,239,000	€ 15,231,000	€ 11,403,000									€ 0
Interest rate risk
Investment [Line Items]
Derivative, nominal amount									€ 529,300,000
Reasonably possible change in risk variable, percent									0.50%	0.50%	0.50%
Currency risk
Investment [Line Items]
Reasonably possible change in risk variable, percent									10.00%	10.00%	10.00%
Currency risk \| Hedges of net investment in foreign operations
Investment [Line Items]
Unrealized foreign exchange loss									€ 1,238,000
Currency risk \| Cross Currency Swap
Investment [Line Items]
Derivative, nominal amount \| $																		$ 30,000,000
Credit Facility Term Loan
Investment [Line Items]
EURIBOR and LIBOR floor									0.00%	0.75%						0.75%	1.00%						1.00%	1.00%
Repayments of non-current borrowings	€ 11,000,000	$ 9,000,000	€ 20,000,000	$ 22,000,000	€ 20,000,000	$ 22,000,000	€ 25,000,000	$ 27,000,000
Credit Facility Term Loan \| Interest rate risk
Investment [Line Items]
EURIBOR and LIBOR floor									0.00%
Minimum reference rates									0.00%
EUR Denominated Credit Facility Term Loan
Investment [Line Items]
EURIBOR and LIBOR floor												0.00%	0.00%	0.00%	0.75%
Term loan, notional amount																							€ 399,000,000
EUR Denominated Credit Facility Term Loan \| Interest rate risk \| Fixed interest rate
Investment [Line Items]
Average rate of hedging instrument																					1.00%	1.00%
EUR Denominated Credit Facility Term Loan \| Interest rate risk \| Euro Interest Rate Cap
Investment [Line Items]
Derivative, nominal amount																					€ 375,000,000
US Denominated Credit Facility Term Loan
Investment [Line Items]
EURIBOR and LIBOR floor														0.00%	0.75%
Term loan, notional amount \| $																								$ 358,000,000
US Denominated Credit Facility Term Loan \| Interest rate risk \| Fixed interest rate
Investment [Line Items]
Average rate of hedging instrument																					2.50%	2.50%
US Denominated Credit Facility Term Loan \| Interest rate risk \| USD Interest Rate Cap
Investment [Line Items]
Derivative, nominal amount \| $																						$ 350,000,000
US Denominated Credit Facility Term Loan \| Currency risk
Investment [Line Items]
Risk exposure associated with instruments sharing characteristic \| $																			$ 180,000,000
Repayments of non-current borrowings									€ 20,000,000
Borrowings									€ 240,495,000	€ 285,558,000
US Denominated Credit Facility Term Loan \| Currency risk \| Fixed interest rate
Investment [Line Items]
Average rate of hedging instrument									1.00%