REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 204,572	$ 414,860
Temporary Staffing Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	195,633	397,002
Other Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	8,939	17,858
Nurse And Allied Staffing Segment [Member]
Disaggregation of Revenue [Line Items]
Revenue	179,339	364,444
Nurse And Allied Staffing Segment [Member] | Temporary Staffing Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	175,690	356,829
Nurse And Allied Staffing Segment [Member] | Other Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	3,649	7,615
Physician Staffing Segment [Member]
Disaggregation of Revenue [Line Items]
Revenue	21,334	42,894
Physician Staffing Segment [Member] | Temporary Staffing Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	19,943	40,173
Physician Staffing Segment [Member] | Other Services [Member]
Disaggregation of Revenue [Line Items]
Revenue	1,391	2,721
Other Human Capital Management Services Segment [Member]
Disaggregation of Revenue [Line Items]
Revenue	3,899	7,522
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	$ 3,899	$ 7,522