CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Apr. 30, 2012	Apr. 30, 2011
Current assets:
Cash and cash equivalents	$ 64,220	$ 62,041
Short-term investments	77,152	126,839
Accounts receivable, net of allowance for doubtful accounts of $921 at April 30, 2012 and $639 at April 30, 2011	56,417	44,376
Unbilled receivables and retentions	27,034	21,966
Inventories, net	43,539	38,137
Deferred income taxes	9,377	6,778
Prepaid expenses and other current assets	4,030	2,372
Total current assets	281,769	302,509
Long-term investments	58,457	6,275
Property and equipment, net	23,515	17,498
Deferred income taxes	5,209	5,284
Other assets	201	181
Total assets	369,151	331,747
Current liabilities:
Accounts payable	20,213	31,134
Wages and related accruals	19,076	15,458
Income taxes payable	8,788	7,404
Customer advances	5,124	1,648
Other current liabilities	9,898	5,736
Liability for uncertain tax positions	606	724
Total current liabilities	63,705	62,104
Wages and related accruals	1,203	762
Deferred rent	1,019	1,275
Liability for uncertain tax positions	4,026	4,138
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-22,243,903 shares at April 30, 2012 and 21,949,884 at April 30, 2011	2	2
Additional paid-in capital	124,954	119,765
Accumulated other comprehensive loss	(694)	(784)
Retained earnings	174,936	144,485
Total stockholders' equity	299,198	263,468
Total liabilities and stockholders' equity	$ 369,151	$ 331,747