Basis of Presentation and Principles of Consolidation - VIE (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) item	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Variable interest entity
Number of professional associations consolidated as VIEs | item	2
Number of professional corporations consolidated as VIEs | item	14
Number of service corporations consolidated as VIEs | item	1
Revenue	$ 180,799	$ 128,573
Net income (loss)	(29,603)	(30,150)
Assets	1,603,077		$ 1,602,827
Deficit	(1,000,177)	(1,001,558)	(1,014,025)	$ (1,013,119)
Primary beneficiary
Variable interest entity
Revenue	42,500	21,100
Net income (loss)	(100)	$ (100)
Assets	22,800		13,600
Liabilities	60,400		51,300
Deficit	$ 37,800		$ 37,700