Earnings Per Share Data

Basic earnings per common share is computed by dividing net income available to common stockholders by the weighted-average number of common shares outstanding for the period. Diluted earnings per share adjusts basic earnings per common share for the effects of potentially dilutive common shares, if the effect is not anti-dilutive. Potentially dilutive common shares include the dilutive effects of shares issuable under the stock option and performance award plans.

The following table reconciles the basic earnings per share computation to the diluted earnings per share computation (in millions, except share and per share amounts):



	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2017		2016		2017		2016
Net income available to common stockholders for purposes of computing basic and diluted earnings per share	$	129.2	$	120.5	$	410.1	$	348.3
Weighted-average number of shares outstanding (in thousands):
Basic shares	104,324		107,621		105,297		107,800
Effect of dilution	354		191		285		199
Diluted shares	104,678		107,812		105,582		107,999
Earnings per share:
Basic earnings per share	$	1.24	$	1.12	$	3.89	$	3.23
Diluted earnings per share	$	1.23	$	1.12	$	3.88	$	3.23

Potentially dilutive shares excluded from the calculation (in thousands):



Stock options excluded as their inclusion would be anti-dilutive	14	34	159	220