Basis of Presentation and Principles of Consolidation - VIE (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) item	Sep. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Variable interest entity
Number of professional associations consolidated as VIEs | item			3
Number of professional corporations consolidated as VIEs | item			12
Revenue	$ 611,402	$ 521,658	$ 1,769,131	$ 1,478,472
Net income (loss)	(73,476)	(84,340)	(9,849,460)	(417,808)
Assets	8,103,965		8,103,965			$ 17,734,608
(Equity) deficit	(6,052,661)	(15,987,582)	(6,052,661)	(15,987,582)	$ (6,084,650)	(16,045,757)	$ (16,001,070)	$ (15,883,804)
Primary beneficiary
Variable interest entity
Revenue	57,500	58,800	176,900	169,600
Net income (loss)	(1,100)	$ 1,000	(3,900)	$ (200)
Assets	51,000		51,000			58,500
Liabilities	91,000		91,000			94,600
(Equity) deficit	$ 40,000		$ 40,000			$ 36,100