Variable Interest Entities (VIEs) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 152,441	$ 103,189	$ 52,726
Restricted cash	0	75
Investment in marketable securities	117,656	116,539
Receivables, net	17,588	11,004
Receivables, net – related party	59,328	48,136
Other receivables	15,919	16,885
Prepaid expenses and other current assets	11,188	10,315
Loans receivable	6,425	6,425
Loans receivable – related parties	0	16,500
Total current assets	380,545	329,068
Noncurrent assets
Intangible assets, net	94,790	103,012
Goodwill	239,053	238,505
Investments in other entities – equity method	26,817	28,427
Restricted cash	746	746
Operating lease right-of-use assets	20,219	14,248
Other assets	22,487	1,681
Total noncurrent assets	452,672	399,645
Total assets	833,217	728,713
Current liabilities
Accounts payable and accrued expenses	24,788	27,279
Fiduciary accounts payable	1,853	2,027
Medical liabilities	70,273	58,725	$ 42,943	$ 33,642
Dividend payable	431	271
Finance lease liabilities	102	102
Operating lease liabilities	3,350	2,990
Total current liabilities	152,507	105,423
Noncurrent liabilities
Deferred tax liability	13,654	18,269
Long-term lease liabilities	355	416
Operating lease liabilities, net of current portion	17,418	11,373
Total noncurrent liabilities	261,882	262,230
Total liabilities	414,389	367,653
Variable Interest Entity, Primary Beneficiary
Current assets
Cash and cash equivalents	113,790	87,110
Restricted cash	0	75
Investment in marketable securities	117,611	123,948
Receivables, net	15,687	9,300
Receivables, net – related party	55,889	42,976
Other receivables	734	744
Prepaid expenses and other current assets	7,752	7,403
Loans receivable	6,425	6,425
Loans receivable – related parties	0	16,500
Total current assets	317,888	294,481
Noncurrent assets
Land, property and equipment, net	9,085	9,547
Intangible assets, net	75,177	81,439
Goodwill	109,460	108,913
Investment in affiliates	285,569	318,315
Investment in privately held entities	36,584	1,615
Investments in other entities – equity method	26,864	28,427
Restricted cash	746	746
Operating lease right-of-use assets	7,017	4,751
Other assets	20,750	1,057
Total noncurrent assets	571,252	554,810
Total assets	889,140	849,291
Current liabilities
Accounts payable and accrued expenses	11,822	11,187
Fiduciary accounts payable	1,853	2,027
Medical liabilities	47,304	49,019
Income taxes payable	42,211	4,530
Amount due to affiliate	21,533	28,058
Dividend payable	431	271
Finance lease liabilities	102	102
Operating lease liabilities	1,319	1,088
Total current liabilities	126,575	96,282
Noncurrent liabilities
Deferred tax liability	9,490	14,059
Long-term lease liabilities	355	416
Operating lease liabilities, net of current portion	5,833	3,742
Total noncurrent liabilities	15,678	18,217
Total liabilities	$ 142,253	$ 114,499