Variable Interest Entities (VIEs) (Details) - USD ($) $ in Thousands		Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents		$ 177,287	$ 193,470	$ 152,441	$ 103,189
Investments in marketable securities		187,206	67,695
Receivables, net		16,540	7,058
Receivables, net – related party		68,767	49,260
Other receivables		4,562	4,297
Prepaid expenses and other current assets		12,188	16,797
Total current assets		470,550	338,577
Noncurrent assets
Intangible assets, net		80,227	86,985
Goodwill		239,053	239,053
Loans receivables – related parties		0	4,145
Investments in other entities – equity method		37,372	43,292
Restricted cash		0	500
Operating lease right-of-use assets		16,928	18,574
Other assets		8,072	18,915
Total noncurrent assets		423,880	478,909
Total assets	[1]	894,430	817,486
Current liabilities
Accounts payable and accrued expenses		53,792	36,143
Fiduciary accounts payable		9,092	9,642
Medical liabilities		59,307	50,330	$ 70,273	$ 58,725
Dividends payable		536	485
Current portion of long-term debt		205	10,889
Finance lease liabilities		110	102
Operating lease liabilities		2,831	3,177
Total current liabilities		128,088	114,992
Noncurrent liabilities
Long-term debt, net of current portion and deferred financing costs		182,705	230,211
Deferred tax liability		21,242	10,959
Finance lease liabilities, net of current portion		249	311
Operating lease liabilities, net of current portion		14,513	15,865
Other long-term liabilities		1,195	0
Total noncurrent liabilities		219,904	257,346
Total liabilities	[1]	347,992	372,338
Variable Interest Entity, Primary Beneficiary
Current assets
Cash and cash equivalents		105,108	126,158
Investments in marketable securities		187,130	67,637
Receivables, net		14,796	5,155
Receivables, net – related party		66,670	46,718
Other receivables		1,814	1,084
Prepaid expenses and other current assets		10,262	14,863
Loan receivable – related party		4,000	0
Amount due from affiliate		16,286	0
Total current assets		406,066	261,615
Noncurrent assets
Land, property and equipment, net		38,770	27,599
Intangible assets, net		64,246	69,250
Goodwill		109,460	109,460
Loans receivables – related parties		114	4,145
Investment in affiliates		683,733	225,144
Investments in other entities – equity method		37,372	43,516
Investment in privately held entities		405	36,584
Restricted cash		0	500
Operating lease right-of-use assets		5,597	6,298
Other assets		1,812	17,177
Total noncurrent assets		941,509	539,673
Total assets		1,347,575	801,288
Current liabilities
Accounts payable and accrued expenses		14,310	12,963
Fiduciary accounts payable		9,092	9,642
Medical liabilities		46,256	37,684
Income taxes payable		1,784	4,225
Dividends payable		536	485
Amount due to affiliate		0	22,698
Current portion of long-term debt		205	201
Finance lease liabilities		110	102
Operating lease liabilities		1,245	1,242
Total current liabilities		73,538	89,242
Noncurrent liabilities
Long-term debt, net of current portion and deferred financing costs		7,390	7,379
Deferred tax liability		20,190	9,144
Finance lease liabilities, net of current portion		249	311
Operating lease liabilities, net of current portion		4,575	5,242
Other long-term liabilities		1,195	0
Total noncurrent liabilities		33,599	22,076
Total liabilities		$ 107,137	$ 111,318

[1] The Company’s consolidated balance sheets include the assets and liabilities of its consolidated VIEs. The consolidated balance sheets include total assets that can be used only to settle obligations of the Company’s consolidated VIEs totaling $1,347.6 million and $801.3 million as of June 30, 2021 and December 31, 2020, respectively, and total liabilities of the Company’s consolidated VIEs for which creditors do not have recourse to the general credit of the primary beneficiary of $107.1 million and $111.3 million as of June 30, 2021 and December 31, 2020, respectively. See Note 15 – Variable Interest Entities (VIEs) for further detail.