Earnings Per Share Earnings Per Share, Narrative (Details) $ / shares in Units, $ in Millions		6 Months Ended
	Apr. 22, 2016 $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2015 USD ($) $ / shares shares	Dec. 31, 2015 $ / shares shares
Tax Asset Rights Plan Series A Preferred [Line Items]
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01		$ 0.01
Preferred Stock, Shares Authorized | shares		5,000,000		5,000,000
Payments of Ordinary Dividends, Common Stock | $		$ 16.3	$ 14.0
Common Stock, Dividends, Per Share, Cash Paid		$ 0.90	$ 0.80
Repurchase of common stock, shares | shares		109,033	552,454
Treasury Stock Acquired, Average Cost Per Share		$ 79.04	$ 75.21
Treasury Stock, Value, Acquired, Cost Method | $		$ 8.6	$ 41.5
Stock Repurchase Program, Remaining Authorized Repurchase Amount | $		$ 114.7
Series A Junior Participating Preferred Stock
Tax Asset Rights Plan Series A Preferred [Line Items]
Preferred Stock, Rights Conversion Ratio into Preferred Stock	1
Preferred Stock, Par or Stated Value Per Share	$ 0.01
Preferred Stock, Shares Authorized | shares	900,000