Stockholders' Equity and Earnings Per Common Share Treasury Stock Transactions (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Equity, Class of Treasury Stock
Number of Treasury Shares Repurchased	2.9	3.2	9.4	9.4
Cost of Shares Repurchased	$ 100.2	$ 115.0	$ 300.3	$ 326.2
Commission Paid on Common Stock Repurchased	0.1		0.2	$ 0.1
Repurchase Program Authorized in May 2016
Equity, Class of Treasury Stock
Authorized Stock Repurchases	750.0		750.0
Remaining Authorized Share Repurchases	598.6		598.6
Repurchase Program Authorized in May 2015
Equity, Class of Treasury Stock
Authorized Stock Repurchases	$ 750.0		$ 750.0