Stockholders' Equity (Roll Forward Of Class A Common Shares Outstanding) (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stockholders' Equity [Abstract]
Balance at the beginning of the year	55,711,325	58,318,983
Repurchases	(4,353,801)	(3,349,286)	(3,173,182)
Stock options, rights and ESPP issuances	593,574	389,799
Restricted share issuances	215,510	375,279
Restricted share forfeitures	(17,138)	(16,252)
Shares withheld for tax obligations	(54,304)	(7,198)
Balance at the end of the period	52,095,166	55,711,325	58,318,983