Stockholders' Equity and Earnings Per Common Share Treasury Stock Transactions (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Equity, Class of Treasury Stock
Number of Treasury Shares Repurchased	3.0	2.9	6.2	5.8
Cost of Shares Repurchased	$ 103.1	$ 100.0	$ 211.2	$ 200.1
Commission Paid on Common Stock Repurchased		$ 0.1	0.1	$ 0.1
Repurchase Program Authorized in May 2015
Equity, Class of Treasury Stock
Authorized Stock Repurchases	750.0		750.0
Remaining Authorized Share Repurchases	717.7		717.7
Repurchase Program Authorized in December 2013
Equity, Class of Treasury Stock
Authorized Stock Repurchases	$ 750.0		$ 750.0