Balance Sheet Parenthetical (Parentheticals) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Class A common shares [Member]
Class of Stock [Line Items]
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	180,000,000	180,000,000
Common Stock, Shares, Issued	64,129,791	57,882,442
Common Stock, Shares, Outstanding	51,522,207	45,359,083
Treasury Stock, Shares	12,607,584	12,523,359
Class B common shares [Member]
Class of Stock [Line Items]
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	30,000,000	30,000,000
Common Stock, Shares, Issued	1,720,839	1,728,952
Common Stock, Shares, Outstanding	1,720,839	1,728,952