Segment Information - Selected Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Segment Reporting Information [Line Items]
Revenue	$ 572,800	$ 489,638	$ 1,624,337	$ 1,435,151
Total costs and expenses	478,328	403,404	1,360,024	1,189,759
Total assets	2,843,930		2,843,930		$ 2,521,164
Depreciation and amortization	19,909	15,213	55,526	51,568
Nonrelated Party
Segment Reporting Information [Line Items]
Shared service fee	2,700		9,900
Related Party
Segment Reporting Information [Line Items]
Shared service fee		3,800		11,500
Reportable Segment
Segment Reporting Information [Line Items]
Revenue	572,800	489,638	1,624,337	1,435,151
Personnel expenses	325,280	277,959	914,404	811,418
Facility expenses	52,561	45,665	152,235	134,508
Other expenses	76,042	64,443	221,104	189,912
Total costs and expenses	453,883	388,067	1,287,743	1,135,838
Segment Adjusted EBITDA	118,917	101,571	336,594	299,313
Total assets	2,843,930	2,481,042	2,843,930	2,481,042
Purchases of property and equipment	21,209	15,145	62,167	47,639
Depreciation and amortization	19,909	15,213	55,526	51,568
Reportable Segment | Nonrelated Party
Segment Reporting Information [Line Items]
Shared service fee	$ 2,700		$ 9,900
Reportable Segment | Related Party
Segment Reporting Information [Line Items]
Shared service fee		$ 3,800		$ 11,500