Comparative Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 01, 2021	Oct. 02, 2020	Jul. 03, 2020	Apr. 03, 2020	Jan. 03, 2020	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Jan. 01, 2021		Jan. 03, 2020		Dec. 28, 2018
Segment Reporting [Abstract]
Revenues before reimbursements	$ 97,330	$ 93,499	$ 87,863	$ 99,720	$ 102,220	$ 95,506	$ 100,263	$ 93,401	$ 378,412		$ 391,390		$ 354,639
Revenues	103,239	98,663	92,045	105,953	110,114	101,548	106,506	99,031	399,900	[1]	417,199	[1]	379,523	[1]
Operating Income	17,734	20,407	9,120	35,988	21,350	23,184	24,823	15,754	83,249		85,111		91,456
Income before income taxes	26,829	24,638	21,414	24,055	26,806	25,211	28,851	23,322
Net income (loss)	$ 21,840	$ 18,084	$ 16,346	$ 26,282	$ 19,121	$ 19,633	$ 20,994	$ 22,712	$ 82,552		$ 82,460		$ 72,254
Net income per share
Basic	$ 0.42	$ 0.35	$ 0.31	$ 0.50	$ 0.36	$ 0.37	$ 0.40	$ 0.43	$ 1.58		$ 1.56		$ 1.37
Diluted	$ 0.41	$ 0.34	$ 0.31	$ 0.49	$ 0.36	$ 0.36	$ 0.39	$ 0.42	$ 1.55		$ 1.53		$ 1.33
Shares used in per share computations
Shares used in basic per share computation	52,402	52,316	52,259	52,575	52,681	52,802	52,745	52,536	52,388		52,691		52,906
Diluted	53,260	53,209	53,139	53,657	53,817	54,002	53,872	53,814	53,323		53,884		54,168

[1] Geographic revenues are allocated based on the location of the client.