Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Receivables related to contracts with customers	$ 75.8	$ 98.0
Receivables related to rental contracts and other	91.9	95.1
Deferred rent revenue	2.5	3.0
Customer deposits	28.8	$ 29.6
Performance obligation satisfied, revenue recognized	$ 23.0
Expected duration	1 year
Benefit period	1 year

Contract With Customer, Commission Benefit Period

No definition available.

Name:	ctos_ContractWithCustomerCommissionBenefitPeriod
Namespace Prefix:	ctos_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Contract With Customer, Liability, Current, Customer Deposits

+ References

No definition available.

+ Details

Name:	ctos_ContractWithCustomerLiabilityCurrentCustomerDeposits
Namespace Prefix:	ctos_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contract With Customer, Liability, Current, Deferred Rent

+ References

No definition available.

+ Details

Name:	ctos_ContractWithCustomerLiabilityCurrentDeferredRent
Namespace Prefix:	ctos_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contract With Customer, Other Receivable, After Allowance For Credit Loss

+ References

No definition available.

+ Details

Name:	ctos_ContractWithCustomerOtherReceivableAfterAllowanceForCreditLoss
Namespace Prefix:	ctos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Contract With Customer, Timing

+ References

No definition available.

+ Details

Name:	ctos_ContractWithCustomerTiming
Namespace Prefix:	ctos_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of revenue recognized arising from contract liability from change in timeframe for performance obligation to be satisfied.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130551-203045

+ Details

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

- Definition

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right to consideration is unconditional.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=126919976&loc=SL49130534-203044

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 310
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=126942793&loc=d3e3073-115593

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=126919976&loc=SL49130531-203044

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130549-203045

+ Details

Name:	us-gaap_ContractWithCustomerReceivableAfterAllowanceForCreditLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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