Stock-Based Compensation - Fair Value Assumptions (Details) - PSUs	3 Months Ended
Mar. 31, 2020 $ / shares
2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	3 years
Dividend yield (%)	1.88%
Expected volatility OEC (%)	33.77%
Expected volatility peer group (%)	17.30%
Correlation	0.4574
Risk-free interest rate (%)	1.45%
Weighted average fair value of PSUs granted (in USD per share)	$ 24.89
2018 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	3 years
Dividend yield (%)	1.94%
Expected volatility OEC (%)	30.22%
Expected volatility peer group (%)	20.09%
Correlation	0.3659
Risk-free interest rate (%)	1.46%
Weighted average fair value of PSUs granted (in USD per share)	$ 39.24
2019 Plan PSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	3 years
Dividend yield (%)	4.65%
Expected volatility OEC (%)	33.30%
Expected volatility peer group (%)	17.62%
Correlation	0.5205
Risk-free interest rate (%)	1.83%
Weighted average fair value of PSUs granted (in USD per share)	$ 11.48

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Correlation

No definition available.

Name:	oec_SharebasedCompensationArrangementbySharebasedPaymentAwardFairValueAssumptionsCorrelation
Namespace Prefix:	oec_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, OEC

+ References

No definition available.

+ Details

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

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Peer Group

+ References

No definition available.

+ Details

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

- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial 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

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oec_TwoThousandSeventeenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oec_TwoThousandEighteenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=oec_TwoThousandNineteenPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: