Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Class A
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	18,717,074	18,099,772
Common stock, shares outstanding	16,335,021	16,414,617
Treasury stock, shares	2,382,053	1,685,155
Class B
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	54,504,294	53,937,394
Common stock, shares outstanding	51,360,645	51,281,512
Treasury stock, shares	3,143,649	2,655,882