Condensed consolidated balance sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Accounts receivable, allowance for bad debts	$ 643	$ 629
Property and equipment, accumulated depreciation	$ 26,285	$ 23,525
Class A Common Stock [Member]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	44,489,000	36,598,000
Common stock, shares outstanding	44,489,000	36,598,000
Class B Common Stock [Member]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	54,080,000	62,112,000
Common stock, shares outstanding	54,080,000	62,112,000