Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total Revenue	$ 365,424	$ 345,558	$ 1,043,652	$ 1,011,157
Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	356,687	333,652	1,019,213	973,987
Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	8,737	11,906	24,439	37,170
Tech
Disaggregation of Revenue [Line Items]
Total Revenue	260,251	271,999	782,785	792,947
Tech | Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	256,118	267,304	770,635	777,227
Tech | Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	4,133	4,695	12,150	15,720
FA
Disaggregation of Revenue [Line Items]
Total Revenue	105,173	73,559	260,867	218,210
FA | Flex revenue
Disaggregation of Revenue [Line Items]
Total Revenue	100,569	66,348	248,578	196,760
FA | Direct Hire revenue
Disaggregation of Revenue [Line Items]
Total Revenue	$ 4,604	$ 7,211	$ 12,289	$ 21,450