Debt Instrument, Discount Rate

No definition available.

Name:	cmps_DebtInstrumentDiscountRate
Namespace Prefix:	cmps_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Temporary Equity, Stock Issued During Period, Shares, Conversion of Debt

+ References

No definition available.

+ Details

Name:	cmps_TemporaryEquityStockIssuedDuringPeriodSharesConversionOfDebt
Namespace Prefix:	cmps_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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

- Definition

For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14172-108612

+ Details

Name:	us-gaap_FairValueOptionChangesInFairValueGainLoss1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_StatementClassOfStockAxis=cmps_ConvertibleBPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_ConvertibleDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_ConvertibleNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Convertible Notes - Narrative (Details) $ in Thousands, £ in Millions		3 Months Ended	9 Months Ended
	Apr. 17, 2020 USD ($) shares	Jun. 30, 2020 shares	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Apr. 17, 2020 GBP (£)	Aug. 28, 2019 USD ($)	Aug. 28, 2019 GBP (£)
Debt Instrument, Redemption [Line Items]
Fair value change of convertible notes \| $			$ 0	$ 1,754
Convertible B preferred stock
Debt Instrument, Redemption [Line Items]
Conversion of notes into B convertible preferred shares (in shares) \| shares	1,723,263	1,723,263
Convertible Debt
Debt Instrument, Redemption [Line Items]
Convertible notes, face amount	$ 18,400				£ 15.0	$ 18,400	£ 15.0
Convertible notes payable
Debt Instrument, Redemption [Line Items]
Convertible notes interest (in percentage)						3.00%	3.00%
Convertible notes, discount of per share price (in percentage)						15.00%	15.00%