Shareholders' Equity - Share Repurchases (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Jul. 28, 2016	Oct. 29, 2015	Dec. 12, 2012
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (in shares)	6,400,000
Repurchases of common stock	$ 462.6	$ 523.2
Common Stock Repurchase 2015 Authorization
Equity, Class of Treasury Stock [Line Items]
Number of shares authorized to be repurchased (in shares)				6,000,000
Stock repurchased during period (in shares)	5,300,000
Remaining authorized repurchase amount (shares)	0
Common Stock Repurchase 2012 Authorization
Equity, Class of Treasury Stock [Line Items]
Number of shares authorized to be repurchased (in shares)					8,000,000
Stock repurchased during period (in shares)		6,000,000
Remaining authorized repurchase amount (shares)	0
Common Stock Repurchase 2016 Authorization
Equity, Class of Treasury Stock [Line Items]
Number of shares authorized to be repurchased (in shares)			6,000,000
Stock repurchased during period (in shares)	1,100,000
Remaining authorized repurchase amount (shares)	5,000,000