Summary of Significant Accounting Policies - Revenue by Vertical Market as Percentage of Total Revenue (Details) - Customer Concentration Risk [Member] - Sales Revenue, Services, Net [Member]	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Concentration Risk [Line Items]
Total revenue	100.00%	100.00%	100.00%
Technology Service Providers [Member]
Concentration Risk [Line Items]
Total revenue	26.70%	31.30%	32.20%
Financial Services [Member]
Concentration Risk [Line Items]
Total revenue	16.20%	15.80%	13.80%
Manufacturing [Member]
Concentration Risk [Line Items]
Total revenue	11.70%	13.50%	16.80%
Energy [Member]
Concentration Risk [Line Items]
Total revenue	5.10%	6.20%	5.20%
General Markets [Member]
Concentration Risk [Line Items]
Total revenue	18.70%	18.30%	15.40%
Healthcare [Member]
Concentration Risk [Line Items]
Total revenue	21.60%	14.90%	16.60%