Percentage of accelerate in vest of awards to number of shares upon termination.

No definition available.

Name:	ccmp_PercentageOfAccelerateVestAwardsToNumberOfShares
Namespace Prefix:	ccmp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period, If the recipient is terminated without cause or resigns with good reason for award will accelerate vest in a number of shares.

+ References

No definition available.

+ Details

Name:	ccmp_PeriodOfTerminationToAccelerateVestAwardsToShares
Namespace Prefix:	ccmp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of vesting installments for awards to be vested from grant date.

+ References

No definition available.

+ Details

Name:	ccmp_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardNumberOfVestingInstallment
Namespace Prefix:	ccmp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of noncash expense for share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

+ Details

Name:	us-gaap_ShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

- Details

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

- Details

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

SHARE-BASED COMPENSATION PLANS - Narrative (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Dec. 31, 2018 USD ($)	Mar. 31, 2020 USD ($) installment	Mar. 31, 2019 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 8,997	$ 11,708
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of vesting installments \| installment		3
Period of Termination to Accelerate Vest Awards to Shares		18 months
Percentage of Accelerate Vest Awards to Number of Shares		150.00%
Stock Option and Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 3,253