CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $)	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Balance at Apr. 30, 2011	$ 263,468,000	$ 2,000	$ 119,765,000	$ 144,485,000	$ (784,000)
Balance (in shares) at Apr. 30, 2011		21,949,884
Increase (Decrease) in Stockholders' Equity
Net income	30,451,000			30,451,000
Unrealized gain (loss) on investments	90,000				90,000
Stock options exercised	565,000		565,000
Stock options exercised (in shares)		141,536
Restricted stock awards (in shares)		157,400
Restricted stock awards forfeited (in shares)		(4,917)
Tax benefit from stock-based compensation	1,428,000		1,428,000
Stock-based compensation	3,196,000		3,196,000
Balance at Apr. 30, 2012	299,198,000	2,000	124,954,000	174,936,000	(694,000)
Balance (in shares) at Apr. 30, 2012		22,243,903
Increase (Decrease) in Stockholders' Equity
Net income	10,426,000			10,426,000
Unrealized gain (loss) on investments	(11,000)				(11,000)
Stock options exercised	289,000		289,000
Stock options exercised (in shares)		208,338
Restricted stock awards (in shares)		163,886
Restricted stock awards forfeited (in shares)		(12,767)
Restricted stock units vested (in shares)		14,926
Tax withholding payment related to net share settlement of equity awards	(77,000)		(77,000)
Tax withholding payment related to net share settlement of equity awards (in shares)		(3,971)
Reclassification from share-based liability compensation to equity	401,000		401,000
Tax benefit from stock-based compensation	1,490,000		1,490,000
Stock-based compensation	3,470,000		3,470,000
Balance at Apr. 30, 2013	315,186,000	2,000	130,527,000	185,362,000	(705,000)
Balance (in shares) at Apr. 30, 2013		22,614,315
Increase (Decrease) in Stockholders' Equity
Net income	13,718,000			13,718,000
Unrealized gain (loss) on investments	442,000				442,000
Stock options exercised	6,709,000		6,709,000
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	(163,000)		(163,000)
Tax withholding payment related to net share settlement of equity awards (in shares)		(4,852)
Tax benefit from stock-based compensation	2,953,000		2,953,000
Stock-based compensation	3,622,000		3,622,000
Balance at Apr. 30, 2014	$ 342,467,000	$ 2,000	$ 143,648,000	$ 199,080,000	$ (263,000)
Balance (in shares) at Apr. 30, 2014		23,176,576