Common Stock (details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Common Stock Number Of Shares Par Value And Other Disclosures Abstract
Treasury Stock Shares	2,100,000
Aggregate Authorized Shares To Repurchase	2,800,000
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