CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Allowance for doubtful accounts receivable	$ 774	$ 576
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000	10,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Class A Common Stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	300,000	300,000
Common stock, shares issued	47,100	37,654
Common stock, shares outstanding	47,100	37,654
Class B Common Stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	215,000	215,000
Common stock, shares issued	28,015	37,236
Common stock, shares outstanding	28,015	37,236