CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	CRA International, Inc. Shareholders' Equity	Common Stock	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interest	Total
Increase (Decrease) in Shareholders' Equity
Cumulative effect of a change in accounting principle | ASU 2016-09	$ 48		$ 48			$ 48
Balance, as adjusted	207,268	$ 54,124	166,962	$ (13,818)	$ 663	207,931
BALANCE at Dec. 31, 2016	207,220	$ 54,124	166,914	(13,818)	663	207,883
BALANCE (in shares) at Dec. 31, 2016		8,333,990
Increase (Decrease) in Shareholders' Equity
Net income	7,624		7,624		77	7,701
Foreign currency translation adjustment	3,922			3,922		3,922
Issuance of common stock	3,044	$ 3,044				3,044
Issuance of common stock (in shares)		89,312
Exercise of stock options	6,420	$ 6,420				6,420
Exercise of stock options (in shares)		293,439
Share-based compensation expense for employees	6,489	$ 6,489				6,489
Restricted shares vesting (in shares)		211,320
Redemption of vested employee restricted shares for tax withholding	(3,262)	$ (3,262)				(3,262)
Redemption of vested employee restricted shares for tax withholding (in shares)		(76,181)
Shares repurchased	(19,528)	$ (19,528)				(19,528)
Shares repurchased (in shares)		(554,708)
Share-based compensation expense for non-employees	127	$ 127				127
Distribution to noncontrolling interest					(419)	(419)
Accrued dividends on unvested shares	(134)		(134)			(134)
Cash paid on dividend equivalents	(121)		(121)			(121)
Cash dividends paid to shareholders (per share)	(4,941)		(4,941)			(4,941)
BALANCE at Dec. 30, 2017	206,908	$ 47,414	169,390	(9,896)	321	207,229
BALANCE (in shares) at Dec. 30, 2017		8,297,172
Increase (Decrease) in Shareholders' Equity
Cumulative effect of a change in accounting principle | ASC 606	366		366			366
Balance, as adjusted	207,274	$ 47,414	169,756	(9,896)	321	207,595
Net income	22,492		22,492		(20)	22,472
Foreign currency translation adjustment	(2,698)			(2,698)		(2,698)
Exercise of stock options	2,166	$ 2,166				2,166
Exercise of stock options (in shares)		100,771
Share-based compensation expense for employees	4,819	$ 4,819				4,819
Restricted shares vesting (in shares)		237,509
Redemption of vested employee restricted shares for tax withholding	(3,946)	$ (3,946)				(3,946)
Redemption of vested employee restricted shares for tax withholding (in shares)		(83,341)
Shares repurchased	(27,616)	$ (27,616)				(27,616)
Shares repurchased (in shares)		(541,631)
GNU gain on sale of business assets and subsequent liquidation					(258)	(258)
Distribution to noncontrolling interest					$ (43)	(43)
Accrued dividends on unvested shares	21		21			21
Cash paid on dividend equivalents	(256)		(256)			(256)
Cash dividends paid to shareholders (per share)	(5,784)		(5,784)			(5,784)
BALANCE at Dec. 29, 2018	196,472	$ 22,837	186,229	(12,594)		$ 196,472
BALANCE (in shares) at Dec. 29, 2018		8,010,480				8,010,480
Increase (Decrease) in Shareholders' Equity
Net income	20,747		20,747			$ 20,747
Foreign currency translation adjustment	831			831		831
Exercise of stock options	3,211	$ 3,211				3,211
Exercise of stock options (in shares)		140,513
Share-based compensation expense for employees and non-employees	3,461	$ 3,461				3,461
Restricted shares vesting (in shares)		128,089
Redemption of vested employee restricted shares for tax withholding	(2,176)	$ (2,176)				(2,176)
Redemption of vested employee restricted shares for tax withholding (in shares)		(43,173)
Shares repurchased	(18,068)	$ (18,068)				(18,068)
Shares repurchased (in shares)		(421,112)
Accrued dividends on unvested shares	58		58			58
Cash paid on dividend equivalents	(246)		(246)			(246)
Cash dividends paid to shareholders (per share)	(6,539)		(6,539)			(6,539)
BALANCE at Dec. 28, 2019	$ 197,751	$ 9,265	$ 200,249	$ (11,763)		$ 197,751
BALANCE (in shares) at Dec. 28, 2019		7,814,797				7,814,797