Net Income Per Common Share

Basic net income per common share is computed by dividing net income by the weighted average number of common shares outstanding during the period. Weighted average common shares outstanding for the basic net income per common share calculation includes certain vested restricted stock units (RSUs) and performance stock units (PSUs) as there are no conditions under which those shares will not be issued. For more information about common share activity during the period, see Note 11, Stockholders' Equity. Diluted net income per common share is computed by dividing net income by the combination of other potentially dilutive weighted average common shares and the weighted average number of common shares outstanding during the period. Other potentially dilutive weighted average common shares include the dilutive effect of stock options, RSUs, and PSUs for each period using the treasury stock method. Under the treasury stock method, the exercise price of a share and the amount of compensation expense, if any, for future service that has not yet been recognized are assumed to be used to repurchase shares in the current period.

The following table sets forth the computation of basic and diluted net income per common share:



	Year Ended December 31
	2017		2016		2015
	(thousands, except per-share data)
Net income	$	82,957	$	38,254	$	52,182
Weighted average common shares outstanding during the period (for basic calculation)	38,623		38,761		39,239
Dilutive effect of other potential common shares	451		164		116
Weighted average common shares and potential common shares (for diluted calculation)	39,074		38,925		39,355

Net income per common share - Basic	$	2.15	$	0.99	$	1.33
Net income per common share - Diluted	$	2.12	$	0.98	$	1.33

The computation of the dilutive effect of other potential common shares excludes stock awards representing no shares, 0.2 million shares, and 0.1 million shares of common stock in the years ended December 31, 2017, 2016, and 2015, respectively. Under the treasury stock method, the inclusion of these stock awards would have been antidilutive.