Stock Repurchases, Dividends and Earnings per Share - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Equity [Abstract]
Stock repurchased and pending settlement (in shares)		0.1	0.2	0.1	0.2
Stock repurchased and pending settlement, liability		$ 2.0	$ 5.9	$ 2.0	$ 5.9
Quarterly dividend declared (in dollars per share)	$ 0.30	$ 0.30	$ 0.28	$ 0.60	$ 0.56
Cash dividends declared				$ 206.2
Quarterly dividend payable		$ 102.8		$ 102.8		$ 103.7