Share Repurchases (Details Textual) (USD $)	1 Months Ended		6 Months Ended
	Feb. 29, 2012	Oct. 31, 2011	Jun. 30, 2012
Class of Stock [Line Items]
Non-voting common stock repurchased	1,821,730
Cost of non-voting common stock repurchased			$ 71,143,000
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
Common Stock Non-Voting [Member]
Class of Stock [Line Items]
Non-voting common stock repurchased	1,821,730
Cost of non-voting common stock repurchased	52,900,000		$ 7,000