11. Earnings per share

The following table presents the calculation of basic and diluted net income per share:

	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands, except share and per share data)	2018		2017		2018		2017
Numerator:
Net income	$	50,144	$	4,616	$	45,236	$	15,101
Interest expense on convertible debt, net of tax		-		835		-		1,742
Amortization of convertible debt issuance costs, net of tax		-		195		-		391
Net income, adjusted	$	50,144	$	5,646	$	45,236	$	17,234

Denominator:
Weighted-average number of shares—basic		49,896,124		41,013,764		49,738,980		40,871,540
Dilutive securities—equity awards		1,266,785		968,354		1,300,215		931,263
Dilutive securities—convertible debt		-		8,096,476		-		8,096,488
Weighted-average number of shares—diluted		51,162,909		50,078,594		51,039,195		49,899,291

Net income per share - basic	$	1.00	$	0.11	$	0.91	$	0.37
Net income per share - diluted	$	0.98	$	0.11	$	0.89	$	0.35

For the three and six months ended June 30, 2018 and 2017, basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the period.

For the three and six months ended June 30, 2018, diluted earnings per share was computed using the "treasury method" by dividing the net income by the weighted average number of shares of common stock outstanding during the period. The weighted average number of shares is adjusted for the potential dilutive effect of the exercise of stock options, and the vesting of restricted stock units and performance stock units.

For the three and six months ended June 30, 2017, diluted earnings per share is computed using the "if-converted" method by dividing the net income adjusted for interest expense and amortization of debt issuance cost, both net of tax, associated with the 2.875% Convertible Senior Notes due 2021 (the "Notes") by the weighted average number of shares of common stock outstanding during the period. The weighted average number of shares is adjusted for the potential dilutive effect of the exercise of stock options; and the vesting of restricted stock units and performance stock units along with the assumption of the conversion of the Notes, at the beginning of the period.

For the three and six months ended June 30, 2018, there were no stock options excluded from the calculation of diluted earnings per share. For the three and six months ended June 30, 2017, approximately 0.4 million stock options were excluded from the calculation of diluted earnings per share due to the fact that the exercise prices were in excess of the average per share closing price during the period.