Common Stock and Treasury Stock (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Common Stock Class A [Member]
Number of common stock issued in connection with stock transactions
Common Stock, Shares, Issued, Beginning Balance	4,771	4,770
Conversion of shares		1
Common Stock, Shares, Issued, Ending Balance	4,771
Common Stock and Treasury Stock (Textual) [Abstract]
Share repurchase program, authorized amount	$ 60
Share repurchase program, remaining authorized amount	$ 14.2
Common Stock Class B [Member]
Number of common stock issued in connection with stock transactions
Common Stock, Shares, Issued, Beginning Balance	597	598
Conversion of shares		(1)
Common Stock, Shares, Issued, Ending Balance	597