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

Number of floors available for lease.

+ References

No definition available.

+ Details

Name:	crai_NumberOfFloorsAvailableForLease
Namespace Prefix:	crai_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- 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

The amount of the annual fixed rent.

+ 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

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

- Definition

Period after which operating lease initial base rent will increase.

+ References

No definition available.

+ Details

Name:	crai_PeriodAfterWhichOperatingLeaseInitialBaseRentWillIncrease
Namespace Prefix:	crai_
Data Type:	xbrli:durationItemType
Balance Type:	na
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
-URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

+ 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

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)
-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-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)
-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

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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

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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

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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

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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

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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

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

- Details

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Commitments and Contingencies (Details) $ in Thousands, £ in Millions								12 Months Ended
	Jul. 11, 2016 USD ($) ft² item	May 20, 2016 GBP (£) ft² floor	Jul. 15, 2015 USD ($) ft² item	Feb. 24, 2015 USD ($) ft² item	Feb. 24, 2014 USD ($) ft² item	Feb. 14, 2008 USD ($) ft²	Nov. 29, 1999 USD ($) ft²	Dec. 31, 2016 USD ($)	Jan. 02, 2016 GBP (£)	Jan. 02, 2016 USD ($)	Jan. 03, 2015 USD ($)	Oct. 26, 2006 ft²
Minimum Rental Commitments
2017								$ 9,078
2018								9,302
2019								9,477
2020								9,198
2021								9,034
Thereafter								50,842
Rental commitments								96,931
Rent expense								10,400		$ 11,600	$ 10,000
Level 3
Minimum Rental Commitments
Contingent acquisition liability								500		$ 800
Standby letters of credit
Minimum Rental Commitments
Amounts outstanding under letters of credit								$ 2,200
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
Rent abatement					$ 1,200
Tenant improvement allowance					4,800
Boston, Massachusetts \| Letters of credit
Minimum Rental Commitments
Amounts outstanding under letters of credit					$ 1,000
Washington, D.C
Minimum Rental Commitments
Number of amendments \| item	6
Lease area \| ft²	6,366						44,932
Annual base rent	$ 300						$ 1,400
Increase in annual base rent (as a percent)	2.25%						2.00%
Rent abatement	$ 200
Tenant improvement allowance	500
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
Number of years of annual base rent			5 years
Increase in annual base rent			$ 2,000
Rent abatement period			10 months
Rent abatement			$ 1,500
Tenant improvement allowance			2,100
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%
Rent abatement period						8 months
Rent abatement						$ 600
Tenant improvement allowance						$ 2,400
London, UK
Minimum Rental Commitments
Lease area \| ft²		23,035										32,168
Number of floors available for lease \| floor		2
Annual base rent \| £		£ 1.6							£ 1.2
Period after which lease rent will increase		5 years