Stockholders' Equity (Share Repurchase Programs) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Stockholders' Equity Note [Abstract]
Shares of common stock repurchased	404,096	511,000	974,096	521,000
Value of common stock repurchased	$ 22.0	$ 20.5	$ 49.0	$ 21.0