Stock Repurchase Program (Details) (USD $) In Millions, except Per Share data	3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2011
Stock Repurchase Program [Abstract]
Stock repurchase during period, shares	0.3	6.2
Stock repurchased during period, value	$ 7.2	$ 137.0
Average price of shares repurchased, per share	$ 21.87	$ 21.94
Amount available under authorized stock repurchase program to repurchase outstanding shares of common stock		$ 153.3