Business Combinations, Assets Held for Sale and Discontinued Operations - Schedule of Management Services Service Line (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Other assets	$ 0	$ 1,641,580
Radiology Services Medical Group [Member]
Assets
Accounts receivable, net	54,284	64,603
Prepaid expenses and other current assets	9,819	9,744
Property and equipment, net	20,078	19,204
Operating leases right-of-use assets	14,165	15,008
Goodwill	640,818	685,170
Intangible assets, net	170,059	180,978
Deferred income tax assets	6,020	18,183
Other assets	36,305	40,724
Total Assets	951,548	1,033,614
Liabilities
Accounts payable and accrued expenses	39,505	42,474
Operating and finance leases	13,619	14,355
Long-term professional liabilities	23,744	21,978
Other liabilities	1,844	81
Total Liabilities	$ 78,712	$ 78,888