Summary of Significant Accounting Policies - Cash and Cash Equivalents (Details)	Jan. 02, 2021 institution
Fair Value Disclosures [Abstract]
Number of financial institutions where cash accounts are concentrated	2

Number of Financial Institutions where Cash Accounts are Concentrated

No definition available.

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