Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Total Revenue	$ 343,020	$ 338,861	$ 678,228	$ 665,599
Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	336,417	325,354	662,526	640,335
Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	6,603	13,507	15,702	25,264
Tech
Disaggregation of Revenue [Line Items]
Total Revenue	255,750	265,305	522,534	520,948
Tech | Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	251,948	259,707	514,517	509,923
Tech | Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	3,802	5,598	8,017	11,025
FA
Disaggregation of Revenue [Line Items]
Total Revenue	87,270	73,556	155,694	144,651
FA | Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	84,469	65,647	148,009	130,412
FA | Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	$ 2,801	$ 7,909	$ 7,685	$ 14,239