Basic earnings per share are computed based on the weighted average number of common shares outstanding. Diluted earnings per share are computed based on the weighted average number of common and dilutive potential common shares outstanding using the treasury stock method. The table shows calculations for basic and diluted earnings per share:



(In millions, except per share data)	Three months ended June 30,				Six months ended June 30,
(In millions, except per share data)	2018		2017		2018		2017
Numerator:
Net income—basic and diluted	$	217	$	100	$	186	$	301
Denominator:
Basic weighted-average common shares outstanding	163.2		164.3		163.6		164.4
Effect of share-based awards:
Stock options	0.8		1.0		0.9		1.1
Nonvested shares	0.5		0.7		0.5		0.7
Diluted weighted-average shares	164.5		166.0		165.0		166.2
Earnings per share:
Basic	$	1.33	$	0.61	$	1.13	$	1.83
Diluted	$	1.32	$	0.60	$	1.12	$	1.81
Number of anti-dilutive share-based awards	1.3		0.6		1.3		0.7

The sources of dilution of our common shares are certain equity-based awards. See our 2017 Annual Report on Form 10-K, Item 8, Note 17, Share-Based Associate Compensation Plans, Page 161, for information about share-based awards. The above table shows the number of anti-dilutive share-based awards for the three and six months ended June 30, 2018 and 2017. These share-based awards were not included in the computation of net income per common share (diluted) because their exercise would have anti-dilutive effects.