Net Income per Common Share (Tables)

3 Months Ended

Mar. 31, 2013

Net Income per Common Share

Computation of basic and diluted earnings per share

	Three Months Ended March 31,
	2012		2013
Numerator:
Net income	$	20,790	$	28,058
Denominator:
Weighted average number of common shares outstanding—basic		27,199		27,110
Common stock equivalents—stock options		432		467
Common stock equivalents—restricted stock		13		17
Common stock equivalents—restricted stock units		102		52
Common stock equivalents—employee stock purchase plan		1		2
Weighted average number of common shares outstanding—diluted		27,747		27,648
Net income per common share—basic	$	0.76	$	1.03
Net income per common share—diluted	$	0.75	$	1.01