Capital Stock (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2009 Class A	Dec. 31, 2009 Class B	Dec. 31, 2011 Class B
Capital Stock
Minimum multiplier for dividend payable on Class A common stock per dividend declared on Class B common stock (as a percent)	67.00%
Percentage of dividend declared on Class B common stock used to determine dividend payable on Class A common stock (as a percent)	67.00%
Capital Stock
Number of shares converted		12,000	(5)
Ratio for converting shares of Class B common stock into shares of Class A common stock, numerator (in Class A shares)				2,400
Ratio for converting shares of Class B common stock into shares of Class A common stock, denominator (in Class B shares)				1