CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Additional Paid-In Capital	Accumulated Deficit	Convertible Preferred Stock	Common Stock Class A	Common Stock Class B	Common Stock Class C	Class D common stock	Total
BALANCE at Dec. 31, 2018	$ 978,628	$ (803,534)		$ 2	$ 3	$ 3	$ 39	$ 175,141
Consolidated net ( loss) Income		8,846						8,846
Repurchase of shares of common stock	(5,321)						(2)	(5,323)
Exercise of options for common stock	29							29
Adjustment of redeemable noncontrolling interests to estimated redemption value	984							984
Issuance of shares	1,609							1,609
Stock-based compensation expense	2,590						2	2,592
BALANCE at Sep. 30, 2019	978,519	(788,885)		2	3	3	39	189,681
Adoption of ASC 842		5,803						5,803
BALANCE at Dec. 31, 2019	979,834	(796,806)	$ 0	2	3	3	39	183,075
Consolidated net ( loss) Income	0	(34,539)	0	0	0	0	0	(34,539)
Repurchase of shares of common stock	(3,604)	0	0	0	0	0	(3)	(3,607)
Exercise of options for common stock	1,974	0	0	0	0	0	2	1,976
Adjustment of redeemable noncontrolling interests to estimated redemption value	(707)	0	0	0	0	0	0	(707)
Issuance of shares	14,770	0	0	2	0	0	0	14,772
Stock-based compensation expense	1,455	0	0	0	0	0	0	1,455
BALANCE at Sep. 30, 2020	$ 993,722	$ (831,345)	$ 0	$ 4	$ 3	$ 3	$ 38	$ 162,425