Segment Data - Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues from services	$ 640,679	$ 374,905	$ 331,827	$ 329,241	$ 215,606	$ 193,968	$ 216,779	$ 210,064		$ 1,676,652	$ 836,417	$ 822,224
Contribution income										210,066	77,788	66,288
Corporate overhead										55,142	51,900	46,246
Depreciation and amortization										9,852	12,671	14,075
Acquisition and integration-related costs										1,068	77	201
Restructuring costs			$ 800	$ 1,200	$ 900	$ 2,300	$ 2,300	$ 600		2,630	6,052	3,571
Legal settlement charges									$ 1,600	0	0	1,600
Impairment charges										2,070	16,248	16,306
Income (loss) from operations										139,304	(9,160)	(15,711)
Nurse And Allied Staffing
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues from services										1,605,781	768,483	747,619
Contribution income										205,738	74,169	63,530
Physician Staffing
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues from services										70,871	67,934	74,605
Contribution income										$ 4,328	$ 3,619	$ 2,758