v3.10.0.1
Stock Repurchases, Dividends and Earnings per Share - Narrative (Details) - USD ($)
$ / shares in Units, $ in Millions
1 Months Ended 3 Months Ended 6 Months Ended
Apr. 30, 2018
Oct. 31, 2017
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Sep. 30, 2017
Equity [Abstract]                
Stock repurchased and pending settlement (in shares)     200,000 100,000 200,000 100,000    
Stock repurchased and pending settlement, liability     $ 10.3 $ 6.6 $ 10.3 $ 6.6    
Additional shares authorized for repurchase, value   $ 2,000.0            
Remaining authorized repurchase amount     $ 1,400.0   $ 1,400.0     $ 98.4
Quarterly dividend declared (in dollars per share) $ 0.345   $ 0.345 $ 0.32 $ 0.69 $ 0.64    
Cash dividends declared         $ 225.7      
Quarterly dividend payable     $ 112.3   $ 112.3   $ 114.4  
Options to purchase common stock (in shares)     0 0 0 0