Capital Stock (Summary of Share Repurchases) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
	Apr. 13, 2017	Mar. 31, 2017
Equity, Class of Treasury Stock [Line Items]
Shares repurchased		0.3
Average price per share		$ 160.81
Aggregate cost		$ 50.7
Authorization remaining at the end of the period		$ 4,125.2
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Shares repurchased	0.2
Average price per share	$ 166.04
Aggregate cost	$ 31.9
Authorization remaining at the end of the period	$ 4,093.3