Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 171,862	$ 119,162
Marketable securities	10,009	27,988
Restricted cash	749	749
Trade receivables, (including related parties of $6,327 and $6,172) net of allowance for doubtful accounts of $5,377 and $3,790	141,697	142,004
Assets held for sale	7,248	2,141
Prepaid expenses and other current assets (including related parties of $274 and $274)	23,345	18,021
Total current assets	354,910	310,065
Property and equipment, net of accumulated depreciation of $190,121 and $191,183	66,375	72,004
Intangible assets subject to amortization, net of accumulated amortization of $107,404 and $103,752 (including related parties of $5,255 and $5,869)	45,760	49,412
Intangible assets not subject to amortization	211,753	216,653
Goodwill	58,043	58,043
Operating leases right of use asset	33,741	33,525
Other assets	7,436	7,643
Total assets	778,018	747,345
Current liabilities
Current maturities of long-term debt	3,000	3,000
Accounts payable and accrued expenses (including related parties of $2,122 and $2,087)	141,767	126,849
Operating lease liabilities	7,524	7,290
Total current liabilities	152,291	137,139
Long-term debt, less current maturities, net of unamortized debt issuance costs of $2,138 and $1,796	208,612	210,454
Long-term operating lease liabilities	31,447	31,775
Other long-term liabilities	3,507	3,732
Deferred income taxes	57,729	54,980
Total liabilities	453,586	438,080
Commitments and contingencies (note 6)
Redeemable noncontrolling interest	37,470	33,285
Stockholders' equity
Additional paid-in capital	826,474	828,813
Accumulated deficit	(538,493)	(551,786)
Accumulated other comprehensive income (loss)	(1,028)	(1,056)
Total stockholders' equity	286,962	275,980
Total liabilities and stockholders' equity	778,018	747,345
Class A common stock
Stockholders' equity
Common stock	6	6
Class B common stock
Stockholders' equity
Common stock	2	2
Class U common stock
Stockholders' equity
Common stock	$ 1	$ 1