CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Apr. 30, 2013	Apr. 30, 2012
Current assets:
Cash and cash equivalents	$ 75,332	$ 64,220
Short-term investments	73,241	77,152
Accounts receivable, net of allowance for doubtful accounts of $936 at April 30, 2013 and $921 at April 30, 2012	19,770	56,417
Unbilled receivables and retentions	11,304	27,034
Inventories, net	62,561	43,539
Income tax receivable	11,777
Deferred income taxes	5,166	7,886
Prepaid expenses and other current assets	4,303	4,030
Total current assets	263,454	280,278
Long-term investments	68,916	58,457
Property and equipment, net	24,429	23,515
Deferred income taxes	5,606	6,700
Other assets	1,060	201
Total assets	363,465	369,151
Current liabilities:
Accounts payable	16,144	20,213
Wages and related accruals	12,116	19,076
Income taxes payable		8,788
Customer advances	7,519	5,124
Other current liabilities	6,408	9,898
Total current liabilities	42,187	63,099
Wages and related accruals		1,203
Deferred rent	771	1,019
Liability for uncertain tax positions	5,321	4,632
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.0001 par value: Authorized shares-10,000,000; none issued or outstanding
Common stock, $0.0001 par value: Authorized shares-100,000,000 Issued and outstanding shares-22,614,315 shares at April 30, 2013 and 22,243,903 at April 30, 2012	2	2
Additional paid-in capital	130,527	124,954
Accumulated other comprehensive loss	(705)	(694)
Retained earnings	185,362	174,936
Total stockholders' equity	315,186	299,198
Total liabilities and stockholders' equity	$ 363,465	$ 369,151