Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total Revenue	$ 363,225	$ 335,208
Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	353,847	326,109
Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	9,378	9,099
Tech
Disaggregation of Revenue [Line Items]
Total Revenue	279,560	266,784
Tech | Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	274,784	262,569
Tech | Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	4,776	4,215
FA
Disaggregation of Revenue [Line Items]
Total Revenue	83,665	68,424
FA | Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	79,063	63,540
FA | Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	$ 4,602	$ 4,884