Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 69,270	$ 33,123
Marketable securities	65,098	91,662
Restricted cash	735	734
Trade receivables, (including related parties of $6,548 and $4,251) net of allowance for doubtful accounts of $3,683 and $2,890	51,706	71,406
Assets held for sale	3,099	950
Prepaid expenses and other current assets (including related parties of $274 and $274)	16,586	11,557
Total current assets	206,494	209,432
Property and equipment, net of accumulated depreciation of $188,749 and $188,579	74,810	79,642
Intangible assets subject to amortization, net of accumulated amortization of $101,713 and $99,819 (including related parties of $6,484 and $7,098)	9,752	16,772
Intangible assets not subject to amortization	216,853	252,544
Goodwill	45,711	46,511
Operating leases right of use asset	35,126	43,837
Other assets	7,428	7,462
Total assets	596,174	656,200
Current liabilities
Current maturities of long-term debt	3,000	3,000
Accounts payable and accrued expenses (including related parties of $1,918 and $2,147)	48,572	53,931
Operating lease liabilities	7,830	9,056
Total current liabilities	59,402	65,987
Long-term debt, less current maturities, net of unamortized debt issuance costs of $2,014 and $2,226	211,736	213,024
Long-term operating lease liabilities	32,784	41,387
Other long-term liabilities	3,385	3,371
Deferred income taxes	38,607	44,259
Total liabilities	345,914	368,028
Commitments and contingencies (note 6)
Stockholders' equity
Additional paid-in capital	830,900	836,170
Accumulated deficit	(581,130)	(547,876)
Accumulated other comprehensive income (loss)	481	(131)
Total stockholders' equity	250,260	288,172
Total liabilities and stockholders' equity	596,174	656,200
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