Forgivable Loans (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Oct. 02, 2021	Jan. 02, 2021
Forgivable loan activity
Beginning balance	$ 61,613	$ 55,141
Advances	9,635	42,418
Reclassifications from accrued expenses or to other assets	(2,229)	(9,713)
Amortization	(18,909)	(26,628)
Effects of foreign currency translation	(61)	395
Ending balance	50,049	61,613
Current portion of forgivable loans	9,662	14,749
Non-current portion of forgivable loans	$ 40,387	$ 46,864

Forgivable Loan Activity

No definition available.

Name:	crai_ForgivableLoanActivityRollForward
Namespace Prefix:	crai_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents information pertaining to forgivable loans provided as on the balance sheet date.

No definition available.

Amounts of increase as a result of advances on loans forgivable.

No definition available.

Name:	crai_ForgivableLoansAdvances
Namespace Prefix:	crai_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents information pertaining to amortizations on forgivable loans during the period.

No definition available.

Name:	crai_ForgivableLoansAmortization
Namespace Prefix:	crai_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The current portion of forgivable loans to employees and non employee experts on the balance sheet date.

No definition available.

Name:	crai_ForgivableLoansCurrent
Namespace Prefix:	crai_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amounts due on long-term loans forgivable on the balance sheet date.

No definition available.

Name:	crai_ForgivableLoansNoncurrent
Namespace Prefix:	crai_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amounts of decrease as a result of reclassification from accrued expenses and reclassification to other assets.

No definition available.

Name:	crai_ForgivableLoansReclassificationFromAccruedExpensesToOtherAssets
Namespace Prefix:	crai_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amounts of increase (decrease) as a result of foreign currency translation on loans forgivable.

No definition available.

Name:	crai_ForgivableLoansTranslationAdjustments
Namespace Prefix:	crai_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration