Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenue	$ 551,631	$ 567,597	$ 1,762,443	$ 1,635,215
Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	382,699	398,417	1,251,509	1,139,883
Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	109,116	143,842	355,580	423,368
Technology and workforce solutions
Segment Reporting Information [Line Items]
Revenue	59,816	25,338	155,354	71,964
Temporary staffing
Segment Reporting Information [Line Items]
Revenue	478,347	521,957	1,562,454	1,504,434
Temporary staffing | Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	382,699	398,417	1,251,509	1,139,883
Temporary staffing | Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	95,648	123,540	310,945	364,551
Temporary staffing | Technology and workforce solutions
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Permanent placement
Segment Reporting Information [Line Items]
Revenue	13,468	20,302	44,635	58,817
Permanent placement | Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Permanent placement | Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	13,468	20,302	44,635	58,817
Permanent placement | Technology and workforce solutions
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Outsourced workforce
Segment Reporting Information [Line Items]
Revenue	38,159	4,643	87,705	12,435
Outsourced workforce | Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Outsourced workforce | Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Outsourced workforce | Technology and workforce solutions
Segment Reporting Information [Line Items]
Revenue	38,159	4,643	87,705	12,435
SaaS-based technologies
Segment Reporting Information [Line Items]
Revenue	21,657	20,695	67,649	59,529
SaaS-based technologies | Nurse and Allied Solutions
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
SaaS-based technologies | Physician and Leadership Solutions
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
SaaS-based technologies | Technology and workforce solutions
Segment Reporting Information [Line Items]
Revenue	$ 21,657	$ 20,695	$ 67,649	$ 59,529