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Summary of Significant Accounting Policies - Goodwill and Intangible Assets (Details) | 12 Months Ended
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Jan. 01, 2022 reporting_unit quarter
Accounting Policies [Abstract] |
Number of reporting units | reporting_unit | 1
Number of trailing quarters used to determine the control premium | quarter | 4

X
- Definition Number of trailing quarters used to determine the control premium utilizing data from publicly available premium studies. + References No definition available. + Details
Name: | crai_NumberOfTrailingQuartersToDetermineControlPremium
Namespace Prefix: | crai_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment. + References No definition available. + Details
Name: | us-gaap_NumberOfReportingUnits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration