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Cover
Nov. 04, 2021
Aug. 05, 2021
Cover [Abstract]    
Document Type 8-K  
Document Period End Date Nov. 04, 2021  
Entity Registrant Name CRA INTERNATIONAL, INC.  
Entity Incorporation, State or Country Code MA  
Entity File Number 000-24049  
Entity Tax Identification Number 04-2372210  
Entity Address, Address Line One 200 Clarendon Street,  
Entity Address, City or Town Boston,  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02116  
City Area Code (617)  
Local Phone Number 425-3000  
Written Communications false  
Soliciting Material false  
Pre-commencement Tender Offer false  
Pre-commencement Issuer Tender Offer false  
Title of 12(b) Security Common Stock, no par value  
Trading Symbol CRAI  
Security Exchange Name NASDAQ  
Entity Emerging Growth Company false  
Entity Central Index Key   0001053706
Amendment Flag   false