Summary of Significant Accounting Policies - Revenue by Vertical Market as Percentage of Total Revenue (Details) - Customer Concentration Risk [Member] - Sales Revenue, Services, Net [Member]	3 Months Ended		6 Months Ended
	Jul. 02, 2021	Jun. 26, 2020	Jul. 02, 2021	Jun. 26, 2020
Concentration Risk [Line Items]
Total revenue	100.00%	100.00%	100.00%	100.00%
Technology Service Providers [Member]
Concentration Risk [Line Items]
Total revenue	28.90%	29.40%	28.60%	31.30%
Manufacturing [Member]
Concentration Risk [Line Items]
Total revenue	12.70%	13.80%	12.60%	14.50%
Financial Services [Member]
Concentration Risk [Line Items]
Total revenue	17.50%	16.00%	17.40%	15.40%
Energy [Member]
Concentration Risk [Line Items]
Total revenue	5.90%	7.50%	5.70%	7.00%
General Markets [Member]
Concentration Risk [Line Items]
Total revenue	20.50%	19.50%	20.70%	18.10%
Healthcare [Member]
Concentration Risk [Line Items]
Total revenue	14.50%	13.80%	15.00%	13.70%