Common Stock (details) (USD $) In Millions	9 Months Ended
	Sep. 30, 2010	Sep. 30, 2011
Common Stock Number Of Shares Par Value And Other Disclosures Abstract
Treasury Stock Shares		2.10
Aggregate Authorized Shares To Repurchase		2.80
Aggregate Authorized Value Of Shares To Repurchase		$ 100.00
Treasury Stock Program	$ 83.30
Date Through Which Entity May Repurchase Stock Under Board Authorization		May 2012