Represents the number of amendments made.

No definition available.

Name:	crai_NumberOfAmendments
Namespace Prefix:	crai_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents number of years of annual base rent applicable before increase in rent.

+ References

No definition available.

+ Details

Name:	crai_NumberOfYearsOfAnnualBaseRent
Namespace Prefix:	crai_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the annual base payments that the lessee is obligated to make in connection with a property under the terms of an agreement classified as an operating lease.

+ References

No definition available.

+ Details

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

- Definition

Represents the increase in annual base rent.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of times by which the lease can be renewed.

+ References

No definition available.

+ Details

Name:	crai_OperatingLeaseNumberOfTimesLeaseCanBeRenewed
Namespace Prefix:	crai_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the percentage increase in annual base rent.

+ References

No definition available.

+ Details

Name:	crai_OperatingLeasePercentageIncreaseInAnnualBaseRent
Namespace Prefix:	crai_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the additional lease area to be taken by the entity.

+ References

No definition available.

+ Details

Name:	crai_OperatingLeasesAdditionalAreaTakenOnLease
Namespace Prefix:	crai_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the additional lease area to be taken by the entity.

+ References

No definition available.

+ Details

Name:	crai_OperatingLeasesAreaTakenOnLease
Namespace Prefix:	crai_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents period of abatement of rent.

+ References

No definition available.

+ Details

Name:	crai_OperatingLeasesRentAbatementPeriod
Namespace Prefix:	crai_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents fixed rent to be paid annually.

+ References

No definition available.

+ Details

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

- Definition

Represents abatement of rent.

+ References

No definition available.

+ Details

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

- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph b
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-Paragraph 6
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+ Details

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

- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

Name:	us-gaap_LeaseAndRentalExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Term of the lessee's leasing arrangement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LesseeLeasingArrangementsOperatingLeasesRenewalTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Sum of the carrying values as of the balance sheet date of the portions of long-term notes payable due within one year or the operating cycle if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 20
-Article 5

+ Details

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

- Definition

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
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-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (a)
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-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

+ Details

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

- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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

- Definition

Amount of cash outflow for the allowance granted to lessee and/or direct costs incurred by lessor used to prepare the leased premises for tenant's occupancy.

+ References

No definition available.

+ Details

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

- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_StatementGeographicalAxis=crai_BostonMassachusettsMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Commitments and Contingencies (Details) $ in Thousands								12 Months Ended
Commitments and Contingencies (Details) $ in Thousands	Jul. 15, 2015 USD ($) ft² item	Jun. 30, 2015 USD ($) ft² item	Feb. 24, 2015 USD ($) ft² item	Feb. 24, 2014 USD ($) ft² item	Feb. 14, 2008 USD ($) ft²	Oct. 26, 2006 USD ($) ft²	Nov. 29, 1999 USD ($) ft²	Jan. 02, 2016 USD ($)	Jan. 03, 2015 USD ($)	Dec. 28, 2013 USD ($)
Minimum Rental Commitments
2016								$ 8,906
2017								8,621
2018								7,648
2019								6,815
2020								6,530
Thereafter								35,956
Rental commitments								74,476
Rent expense								11,600	$ 10,000	$ 9,600
NeoCo outstanding debt								75
Level 3
Minimum Rental Commitments
Contingent acquisition liability								773	$ 316
Standby letters of credit
Minimum Rental Commitments
Amounts outstanding under letters of credit								2,500
Boston, Massachusetts
Minimum Rental Commitments
Lease area \| ft²			67,659	57,602
Number of times, lease can be renewed \| item			1	2
Lease extension term			3 years	5 years
Annual base rent				$ 2,400
Increase in annual base rent (as a percent)				2.00%
Additional lease area \| ft²			10,057
Annual fixed rent			$ 500
Tenant improvement allowance				$ 4,800
Rent abatement				1,200
Boston, Massachusetts \| Letters of credit
Minimum Rental Commitments
Amounts outstanding under letters of credit				$ 1,000
Washington, D.C
Minimum Rental Commitments
Lease area \| ft²		33,258					44,932
Annual base rent		$ 1,400					$ 1,400
Increase in annual base rent (as a percent)		2.25%					2.00%
Number of amendments \| item		5
Tenant improvement allowance		$ 2,800
Rent abatement		2,300
Washington, D.C \| Letters of credit
Minimum Rental Commitments
Amounts outstanding under letters of credit		$ 200
New York, New York
Minimum Rental Commitments
Lease area \| ft²	25,261
Number of times, lease can be renewed \| item	1
Lease extension term	5 years
Annual base rent	$ 1,800
Tenant improvement allowance	2,100
Rent abatement	$ 1,500
Number of years of annual base rent	5 years
Increase in annual base rent	$ 2,000
Rent abatement period	10 months
New York, New York \| Letters of credit
Minimum Rental Commitments
Amounts outstanding under letters of credit	$ 900
Chicago, Illinois
Minimum Rental Commitments
Lease area \| ft²					36,570
Annual base rent					$ 1,000
Increase in annual base rent (as a percent)					2.50%
Tenant improvement allowance					$ 2,400
Rent abatement					$ 600
Rent abatement period					8 months
London, UK
Minimum Rental Commitments
Lease area \| ft²						32,168
Annual base rent						$ 1,800		$ 1,200