Common Stock Repurchase Program - Additional Information (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				1 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Additional Paid-in Capital	Mar. 31, 2013 Retained Earnings	Mar. 31, 2013 Common Stock Repurchase Program	Oct. 27, 2011 Common Stock Repurchase Program
Share Repurchases [Line Items]
Repurchase of common stock, common stock authorized					$ 150.0
Repurchase of common stock, shares repurchased	0.1
Repurchase of common stock, average price per share	$ 32.47
Repurchase of common stock, aggregate purchase price	2.4	0.7	1.7
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 92.6