Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Total Revenue	$ 403,614	$ 343,020	$ 766,839	$ 678,228
Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	391,362	336,417	745,209	662,526
Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	12,252	6,603	21,630	15,702
Tech
Disaggregation of Revenue [Line Items]
Total Revenue	310,728	255,750	590,288	522,534
Tech | Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	304,645	251,948	579,429	514,517
Tech | Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	6,083	3,802	10,859	8,017
FA
Disaggregation of Revenue [Line Items]
Total Revenue	92,886	87,270	176,551	155,694
FA | Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	86,717	84,469	165,780	148,009
FA | Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	$ 6,169	$ 2,801	$ 10,771	$ 7,685