Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Reconciliation of Basic and Diluted Earnings Per Share Computations

The following table provides a reconciliation of basic and diluted earnings per share computations for the years ended December 31, 2019, 2018 and 2017 (in millions, except per share amounts): 

	Years ended December 31,
(Millions of dollars except per share amounts)	2019		2018		2017
Earnings per common share:
Net income per share - basic
Net income attributable to common stockholders	$	154.8	$	213.6	$	245.3
Weighted average common shares outstanding (in thousands)	31,594		32,674		35,816
Earnings per common share	$	4.90	$	6.54	$	6.85
Earnings per common share - assuming dilution:
Net income per share - diluted
Net income attributable to common stockholders	$	154.8	$	213.6	$	245.3
Weighted average common shares outstanding (in thousands)	31,594		32,674		35,816
Common equivalent shares:
Share-based awards	264		309		340
Weighted average common shares outstanding - assuming dilution (in thousands)	31,858		32,983		36,156
Earnings per common share assuming dilution	$	4.86	$	6.48	$	6.78