Share Repurchases (Details Textual) (USD $)	1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended
	Oct. 31, 2011	Mar. 31, 2012	Feb. 29, 2012 Common Stock Non-Voting [Member]	Mar. 31, 2012 Common Stock Non-Voting [Member]
Class of Stock [Line Items]
Non-voting common stock repurchased		1,821,730	1,821,730
Cost of non-voting common stock repurchased		$ 71,116,000	$ 52,900,000	$ 7,000
Share Repurchases (Textual) [Abstract]
Authorized a share repurchase program	35,000,000
Common stock shares repurchased		820,894
Cost of common stock shares repurchased		$ 25,200,000