Earnings Per Share

3 Months Ended

Mar. 31, 2013

Earnings Per Share

10. Earnings Per Share

Basic earnings per share is calculated by dividing net income by the weighted average number of shares outstanding during the reported period. The calculation of diluted earnings per share is similar to basic earnings per share, except that the weighted average number of shares outstanding includes the dilution from potential shares resulting from stock options and unvested restricted stock awards.

The components of basic and diluted earnings per share are as follows:

	Three Months Ended
	March 31,
In millions, except per share amounts	2013		2012
Net income available for common stockholders	$	59	$	91
Weighted average outstanding shares of common stock		165.4		167.9
Dilutive effect of employee stock options and restricted stock		3.1		3.7
Common stock and common stock equivalents		168.5		171.6
Earnings per share:
Basic	$	0.36	$	0.54
Diluted	$	0.35	$	0.53

Because the average market price of common shares for the periods was greater than the exercise prices of outstanding awards, no stock options were excluded from the computation of diluted earnings per share for the three months ended March 31, 2013, and March 31, 2012.