CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - 6 months ended Jun. 30, 2018 - USD ($) $ in Thousands	Total	Convertible Preferred Stock [Member]	Common Class A [Member]	Common Class B [Member]	Common Class C [Member]	Common Class D [Member]	Additional Paid-In Capital	Accumulated Deficit [Member]
BALANCE, as of December 31, 2017 at Dec. 31, 2017	$ 42,655	$ 0	$ 2	$ 3	$ 3	$ 41	$ 983,582	$ (940,976)
Consolidated net income	1,035	0	0	0	0	0	0	1,035
Repurchase of 232 shares of Class A common stock and 2,339,005 shares of Class D common stock	(4,568)	0	0	0	0	(2)	(4,566)	0
Repurchase of share-based equity awards	(1,077)	0	0	0	0	0	(1,077)	0
Exercise of options for 58,190 shares of common stock	85	0	0	0	0	0	85	0
Adjustment of redeemable noncontrolling interests to estimated redemption value	(622)	0	0	0	0	0	(622)	0
Stock-based compensation expense	2,501	0	0	0	0	1	2,500	0
BALANCE, as of June 30, 2018 at Jun. 30, 2018	$ 40,009	$ 0	$ 2	$ 3	$ 3	$ 40	$ 979,902	$ (939,941)