Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Treasury stock, shares	244,113	243,040
Class A Common Stock [Member]
Common stock, par value	0.01	0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	23,882,331	23,396,549
Common stock, shares outstanding	23,638,218	23,153,509
Class B Common Stock [Member]
Common stock, par value	0.01	0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	13,192,845	13,275,345
Common stock, shares outstanding	13,192,845	13,275,345