Segment Information - Reconciliation of Revenue and Segment Operating Income by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 551,631	$ 567,597	$ 1,762,443	$ 1,635,215
Segment operating income	46,462	39,739	120,606	129,947
Depreciation and amortization	26,936	17,085	69,096	41,513
Depreciation (included in cost of revenue)	481	0	981	0
Share-based compensation	3,772	2,825	15,046	11,713
Interest expense, net, and other	12,564	7,830	35,061	19,568
Income before income taxes	33,898	31,909	85,545	110,379
Nurse and allied solutions
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	382,699	398,417	1,251,509	1,139,883
Physician and leadership solutions
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	109,116	143,842	355,580	423,368
Technology and workforce solutions
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	59,816	25,338	155,354	71,964
Operating segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	551,631	567,597	1,762,443	1,635,215
Segment operating income	94,141	81,506	281,952	244,266
Operating segments | Nurse and allied solutions
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	382,699	398,417	1,251,509	1,139,883
Segment operating income	52,923	52,533	173,706	158,841
Operating segments | Physician and leadership solutions
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	109,116	143,842	355,580	423,368
Segment operating income	15,538	17,547	45,432	52,280
Operating segments | Technology and workforce solutions
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	59,816	25,338	155,354	71,964
Segment operating income	25,680	11,426	62,814	33,145
Unallocated corporate overhead
Segment Reporting, Revenue Reconciling Item [Line Items]
Unallocated corporate overhead	$ 16,490	$ 21,857	$ 76,223	$ 61,093