SEGMENT DATA - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Number of operating segments | segment			2
Revenue from services	$ 374,905	$ 193,968	$ 1,035,973	$ 620,811
Contribution loss	(41,555)	(18,752)	(116,246)	(54,011)
Nurse and Allied Staffing
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	356,139	177,516	985,335	569,306
Contribution loss	$ (40,645)	(17,925)	$ (113,346)	(51,334)
Nurse and Allied Staffing | Revision of Prior Period, Adjustment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services		2,300		7,700
Contribution loss		$ 300		$ 1,700