SEGMENT DATA - Information on Operating Segments and Reconciliation to Loss From Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	$ 374,905	$ 193,968	$ 1,035,973	$ 620,811
Contribution income	41,555	18,752	116,246	54,011
Corporate overhead	12,049	12,499	40,326	36,993
Depreciation and amortization	2,680	3,247	7,132	10,472
Acquisition and integration-related costs	61	0	985	77
Restructuring costs	318	2,316	2,391	5,210
Impairment charges	0	1,071	2,070	16,082
Income (loss) from operations	26,447	(381)	63,342	(14,823)
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 income	40,645	17,925	113,346	51,334
Physician Staffing
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue from services	18,766	16,452	50,638	51,505
Contribution income	$ 910	$ 827	$ 2,900	$ 2,677