XML 48 R37.htm IDEA: XBRL DOCUMENT v3.19.1
Net Income Per Share of Class A and Class B Common Stock (Earnings Per Share Reconciliation) (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]    
Weighted average common shares outstanding - basic (in shares) 23.2 25.1
Weighted average common shares outstanding - diluted (in shares) 23.2 25.2
Net income per common share - basic (in dollars per share) $ 2.43 $ 2.08
Net income per common share - diluted (in dollars per share) $ 2.42 $ 2.07
Class A common stock    
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]    
Net income applicable to common stockholders - basic $ 54.4 $ 50.0
Reallocation of net income due to conversion of Class B to Class A common shares outstanding 0.3 0.3
Conversion of Class B common shares into Class A common shares 1.7 1.8
Net income applicable to common stockholders - diluted $ 56.4 $ 52.1
Weighted average common shares outstanding - basic (in shares) 22.3 24.1
Conversion of Class B common shares into Class A common shares (in shares) 0.8 1.0
Effect of dilutive stock options on weighted average common shares (in shares) 0.1 0.1
Weighted average common shares outstanding - diluted (in shares) 23.2 25.2
Net income per common share - basic (in dollars per share) $ 2.43 $ 2.08
Net income per common share - diluted (in dollars per share) $ 2.42 $ 2.07
Class B common stock    
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]    
Net income applicable to common stockholders - basic $ 2.0 $ 2.1
Reallocation of net income due to conversion of Class B to Class A common shares outstanding 0.0 0.0
Conversion of Class B common shares into Class A common shares 0.0 0.0
Net income applicable to common stockholders - diluted $ 2.0 $ 2.1
Weighted average common shares outstanding - basic (in shares) 0.8 1.0
Conversion of Class B common shares into Class A common shares (in shares) 0.0 0.0
Effect of dilutive stock options on weighted average common shares (in shares) 0.0 0.0
Weighted average common shares outstanding - diluted (in shares) 0.8 1.0
Net income per common share - basic (in dollars per share) $ 2.43 $ 2.08
Net income per common share - diluted (in dollars per share) $ 2.42 $ 2.07