Earnings Per Share Earnings Per Share, Narrative (Details) $ / shares in Units, $ in Millions		9 Months Ended
	Apr. 07, 2016	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares	Apr. 22, 2016 $ / 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 | $		$ 24.4	$ 21.0
Common Stock, Dividends, Per Share, Cash Paid		$ 1.35	$ 1.20
Repurchase of common stock, shares | shares		170,304	599,397
Treasury Stock Acquired, Average Cost Per Share		$ 81.04	$ 75.81
Treasury Stock, Value, Acquired, Cost Method | $		$ 13.8	$ 45.4
Stock Repurchase Program, Remaining Authorized Repurchase Amount | $		$ 109.5
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