Revenue and Allowances - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 01, 2022	Jan. 02, 2021	Dec. 28, 2019
Disaggregation of Revenue
Consulting services revenues	$ 565,933	$ 508,373	$ 451,370
United States
Disaggregation of Revenue
Consulting services revenues	451,436	405,808	357,156
United Kingdom
Disaggregation of Revenue
Consulting services revenues	86,191	79,922	72,169
Other
Disaggregation of Revenue
Consulting services revenues	28,306	22,643	22,045
Fixed-price
Disaggregation of Revenue
Consulting services revenues	136,276	124,383	107,344
Time-and-materials
Disaggregation of Revenue
Consulting services revenues	$ 429,657	$ 383,990	$ 344,026

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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+ Details