Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Revenue	$ 602,461	$ 532,441
Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	424,346	373,472
Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	137,842	137,077
Technology and Workforce Solutions
Segment Reporting Information [Line Items]
Revenue	40,273	21,892
Temporary staffing
Segment Reporting Information [Line Items]
Revenue	512,267	455,869
Temporary staffing | Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	392,671	337,029
Temporary staffing | Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	119,596	118,840
Temporary staffing | Technology and Workforce Solutions
Segment Reporting Information [Line Items]
Revenue	0	0
Permanent placement
Segment Reporting Information [Line Items]
Revenue	18,246	18,237
Permanent placement | Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	0	0
Permanent placement | Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	18,246	18,237
Permanent placement | Technology and Workforce Solutions
Segment Reporting Information [Line Items]
Revenue	0	0
Outsourced workforce
Segment Reporting Information [Line Items]
Revenue	49,355	40,138
Outsourced workforce | Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	31,675	36,443
Outsourced workforce | Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	0	0
Outsourced workforce | Technology and Workforce Solutions
Segment Reporting Information [Line Items]
Revenue	17,680	3,695
SaaS-based technologies
Segment Reporting Information [Line Items]
Revenue	22,593	18,197
SaaS-based technologies | Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	0	0
SaaS-based technologies | Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	0	0
SaaS-based technologies | Technology and Workforce Solutions
Segment Reporting Information [Line Items]
Revenue	$ 22,593	$ 18,197