13. Loss per share

Basic loss per share is computed by dividing net loss for the period by the weighted average number of common stock outstanding during the period. Diluted loss per share is computed by dividing net loss for the period by the weighted average number of shares of common stock and potentially dilutive common stock outstanding during the period. The dilutive effect of outstanding options and equity incentive awards is reflected in diluted loss per share by application of the treasury stock method. The calculation of diluted loss per share excludes all anti-dilutive common shares. The following table sets forth the computation of basic and diluted loss per share for the three and six months ended June 30, 2018 and 2017.

(U.S. dollars in millions, except per share amounts)	Three Months Ended June 30						Six Months Ended June 30
	2018			2017			2018			2017
Numerator:
Basic and diluted:
Net loss attributable to common shareholders	$	(63	)	$	(28	)	$	(95	)	$	(48	)

Denominator:
Basic: Weighted average number of shares outstanding (in millions)		87.13			87.13			87.13			87.13
Diluted: Weighted-average number of shares outstanding, assuming dilution (in millions)¹	87.13			87.13			87.13			87.13

Basic loss per share	$	(0.72	)	$	(0.32	)	$	(1.09	)	$	(0.55	)
Diluted loss per share	$	(0.72	)	$	(0.32	)	$	(1.09	)	$	(0.55	)

¹ Shares in the diluted EPS calculation represent basic shares due to the net loss. The shares excluded from the calculation were 598,568 for the three and six months ended June 30, 2018 and 2017 because they are anti-dilutive.