CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Operating activities
Net income	$ 13,718	$ 10,426	$ 30,451
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	9,155	10,937	8,973
Pre-tax impairment charges	3,317
Provision for doubtful accounts	(6)	462	291
Unrealized foreign currency gain	21
Gain on sale of equity securities	(4)
Deferred income taxes	(3,110)	3,851	(2,579)
Change in fair value of conversion feature of convertible bonds	(1,773)	(6,173)
Stock-based compensation	3,622	3,470	3,196
Tax benefit from exercise of stock options	2,305	1,606	1,239
Excess tax benefit from stock-based compensation	(648)		(189)
Loss (gain) on disposition of property and equipment		18	(11)
Changes in operating assets and liabilities:
Accounts receivable	(11,963)	36,185	(12,332)
Unbilled receivables and retentions	375	15,730	(5,068)
Inventories	11,862	(19,022)	(5,402)
Income tax receivable	5,193	(11,777)
Prepaid expenses and other assets	82	(317)	(1,678)
Accounts payable	(2,238)	(4,069)	(10,921)
Other liabilities	(1,045)	(17,320)	12,784
Net cash provided by operating activities	28,863	24,007	18,754
Investing activities
Acquisition of property and equipment	(7,143)	(11,834)	(14,992)
Net redemptions (purchases) of held-to-maturity investments	23,113	2,014	(2,575)
Acquisition of intangible assets	(750)	(850)
Purchases of available-for-sale investments		(3,037)
Sales of available-for-sale investments	360	600	225
Proceeds from sale of property and equipment			13
Net cash provided by (used in) investing activities	15,580	(13,107)	(17,329)
Financing activities
Excess tax benefit from stock-based compensation	648		189
Tax withholding payment related to net settlement of equity awards	(163)	(77)
Exercise of stock options	6,709	289	565
Net cash provided by financing activities	7,194	212	754
Net increase in cash and cash equivalents	51,637	11,112	2,179
Cash and cash equivalents at beginning of year	75,332	64,220	62,041
Cash and cash equivalents at end of year	126,969	75,332	64,220
Cash paid during the year for:
Income taxes	2,556	15,262	13,104
Unrealized gain (loss) on long-term investments recorded in accumulated other comprehensive loss, net of deferred taxes of $261, $37 and $56, respectively	442	(11)	90
Reclassification from share-based liability compensation to equity		$ 401