Amount of expense (income) related to adjustment to fair value of warrant outstanding liability.

No definition available.

Name:	clnn_FairValueAdjustmentOfWarrantsOutstanding
Namespace Prefix:	clnn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

It represents the amount of loss in fair value of warrant liability.

+ References

No definition available.

+ Details

Name:	clnn_LossInFairValueOfWarrantLiability
Namespace Prefix:	clnn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percent of fully-diluted equity purchasable upon exercise.

+ References

No definition available.

+ Details

Name:	clnn_PercentOfFullydilutedEquityPurchasableUponExercise
Namespace Prefix:	clnn_
Data Type:	dtr:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	clnn_PreferredStockWarrantLiabilityDetailsLineItems
Namespace Prefix:	clnn_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Shares of warrants exercisable.

+ References

No definition available.

+ Details

Name:	clnn_SharesOfWarrantsExercisable
Namespace Prefix:	clnn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Per share decrease in exercise price of warrant. Excludes change due to standard antidilution provision.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21475-112644

+ Details

Name:	us-gaap_WarrantExercisePriceDecrease
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Period between issuance and expiration of outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Details

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

- Details

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

Preferred Stock Warrant Liability (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
	Aug. 11, 2020	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Apr. 08, 2013
Preferred Stock Warrant Liability (Details) [Line Items]
Loss in fair value of warrant liability				$ 14.6
Fair value of the outstanding warrants		$ 5.1	$ 7.4
Series A Preferred Stock [Member]
Preferred Stock Warrant Liability (Details) [Line Items]
Warrants expire						10 years
Exercise price					$ 1.97
Shares of warrants exercisable					1,608,670
Series C Preferred Stock [Member]
Preferred Stock Warrant Liability (Details) [Line Items]
Exercise price					$ 1.97
Shares of warrants exercisable					271,439
Percent of fully-diluted equity purchasable upon exercise						0.25%
Series D Preferred Stock [Member]
Preferred Stock Warrant Liability (Details) [Line Items]
Exercise price	$ 1.97
Shares of warrants exercisable	320,441