Net Income Per Share (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Net income available to common shareholders
Net income attributable to CRA as reported	$ 6,859	$ 3,908	$ 6,839	$ 4,886	$ 20,747	$ 22,492	$ 7,624
Less: net income attributable to participating shares					55	108	51
Net income available to common shareholders					$ 20,692	$ 22,384	$ 7,573
Reconciliation of basic to diluted weighted average shares of common stock outstanding
Basic weighted average shares outstanding					7,866,000	8,107,000	8,292,000
Stock options and restricted stock units					301,000	463,000	205,000
Diluted weighted average shares outstanding					8,167,000	8,570,000	8,497,000
Calculation of common stock equivalents for purposes of computing diluted weighted average shares outstanding
Anti-dilutive securities excluded from EPS computation (in shares)					62,367	29,612	75,004