Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Class A
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	12,000,000	12,000,000
Common Stock, shares issued	6,595,308	6,595,308
Common Stock, shares outstanding	6,595,308	6,595,308
Class B
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	150,000,000	150,000,000
Common Stock, shares issued	86,947,407	89,348,958
Common Stock, shares outstanding	86,947,407	89,348,958
Class C
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	1,200,000	1,200,000
Common Stock, shares issued	663,940	663,940
Common Stock, shares outstanding	663,940	663,940
Class D
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	5,000,000	5,000,000
Common Stock, shares issued	20,868	22,100
Common Stock, shares outstanding	20,868	22,100