REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 200,717	$ 615,577
Temporary Staffing Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	192,462	589,464
Other Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,255	26,113
Nurse And Allied Staffing Segment [Member]
Disaggregation of Revenue [Line Items]
Revenue	176,344	540,788
Nurse And Allied Staffing Segment [Member] | Temporary Staffing Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	172,819	529,648
Nurse And Allied Staffing Segment [Member] | Other Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	3,525	11,140
Physician Staffing Segment [Member]
Disaggregation of Revenue [Line Items]
Revenue	21,158	64,052
Physician Staffing Segment [Member] | Temporary Staffing Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	19,643	59,816
Physician Staffing Segment [Member] | Other Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,515	4,236
Other Human Capital Management Services Segment [Member]
Disaggregation of Revenue [Line Items]
Revenue	3,215	10,737
Other Human Capital Management Services Segment [Member] | Temporary Staffing Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	0	0
Other Human Capital Management Services Segment [Member] | Other Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 3,215	$ 10,737