10. Earnings per share

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

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands, except share and per share data)	2018		2017		2018		2017
Numerator:
Net income	$	20,945	$	33,551	$	66,181	$	48,652
Interest expense on convertible debt, net of tax		-		704		-		2,445
Amortization of convertible debt issuance costs, net of tax		-		195		-		586
Net income, adjusted	$	20,945	$	34,450	$	66,181	$	51,683

Denominator:
Weighted-average number of shares—basic		50,071,632		41,222,504		49,851,082		40,989,813
Dilutive securities—equity awards		1,415,364		1,148,857		1,338,598		1,003,794
Dilutive securities—convertible debt		-		8,096,468		-		8,096,481
Weighted-average number of shares—diluted		51,486,996		50,467,829		51,189,680		50,090,088

Net income per share - basic	$	0.42	$	0.81	$	1.33	$	1.19
Net income per share - diluted	$	0.41	$	0.68	$	1.29	$	1.03

For the three and nine months ended September 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 nine months ended September 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 nine months ended September 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. The Company terminated the conversion rights under the Notes during the fourth quarter of 2017.

For the three and nine months ended September 30, 2018 and 2017, there were no stock options excluded from the calculation of diluted earnings per share.