CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Total
Balance at Apr. 30, 2013	$ 2	$ 130,527	$ 185,362	$ (705)	$ 315,186
Balance (in shares) at Apr. 30, 2013	22,614,315
Increase (Decrease) in Stockholders' Equity
Net income			13,718		13,718
Unrealized gain (loss) on investments				442	442
Stock options exercised		6,709			6,709
Stock options exercised (in shares)	460,231
Restricted stock awards (in shares)	128,500
Restricted stock awards forfeited (in shares)	(35,869)
Restricted stock units vested (in shares)	14,251
Tax withholding payment related to net share settlement of equity awards		(163)			(163)
Tax withholding payment related to net share settlement of equity awards (in shares)	(4,852)
Tax benefit from stock-based compensation		2,953			2,953
Stock-based compensation		3,622			3,622
Balance at Apr. 30, 2014	$ 2	143,648	199,080	(263)	342,467
Balance (in shares) at Apr. 30, 2014	23,176,576
Increase (Decrease) in Stockholders' Equity
Net income			2,895		2,895
Unrealized gain (loss) on investments				(1,095)	(1,095)
Stock options exercised		722			722
Stock options exercised (in shares)	35,018
Restricted stock awards (in shares)	160,180
Restricted stock awards forfeited (in shares)	(56,004)
Tax withholding payment related to net share settlement of equity awards		(36)			(36)
Tax withholding payment related to net share settlement of equity awards (in shares)	(1,130)
Tax benefit from stock-based compensation		191			191
Stock-based compensation		3,768			3,768
Balance at Apr. 30, 2015	$ 2	148,293	201,975	(1,358)	348,912
Balance (in shares) at Apr. 30, 2015	23,314,640
Increase (Decrease) in Stockholders' Equity
Net income			8,966		8,966
Unrealized gain (loss) on investments				27	27
Reclassifications out of accumulated other comprehensive loss				1,130	1,130
Stock options exercised		1,122			1,122
Stock options exercised (in shares)	84,881
Restricted stock awards (in shares)	191,548
Restricted stock awards forfeited (in shares)	(46,753)
Tax withholding payment related to net share settlement of equity awards		(29)			(29)
Tax withholding payment related to net share settlement of equity awards (in shares)	(1,130)
Reclassification from share-based liability compensation to equity		228			228
Tax benefit from stock-based compensation		98			98
Purchases of common stock for retirement			(3,756)		(3,756)
Purchases of common stock for retirement (in shares)	(183,261)
Stock-based compensation		4,562			4,562
Balance at Apr. 30, 2016	$ 2	$ 154,274	$ 207,185	$ (201)	$ 361,260
Balance (in shares) at Apr. 30, 2016	23,359,925