Consolidated Statements Of Changes In Shareholders' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Stockholders' Equity [Abstract]
Dividends per share (in dollars per share)	$ 1.20	$ 1.20	$ 1.20
Common Class A [Member]
Statement of Stockholders' Equity [Abstract]
Repurchase of shares (shares)	56,276	112,471
Common Class B [Member]
Statement of Stockholders' Equity [Abstract]
Repurchase of shares (shares)	606,929	37,863