CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Operating activities
Net income	$ 8,966	$ 2,895	$ 13,718
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	6,074	8,366	9,155
Loss from equity method investments	138	240	30
Impairment of available-for-sale securities	2,186
Impairment of long-lived assets		438	3,317
Provision for doubtful accounts	(178)	(106)	(6)
Losses on foreign currency transactions	63	580	21
Loss (gain) on sale of equity securities	219	209	(4)
Deferred income taxes	(2,912)	(3,382)	(3,110)
Change in fair value of conversion feature of convertible bonds		(73)	(1,773)
Stock-based compensation	4,562	3,768	3,622
Tax benefit from exercise of stock options	161	52	2,305
Excess tax benefit from stock-based compensation	(39)	(162)	(648)
(Gain) loss on disposition of property and equipment	(22)	3,661
Amortization of held-to-maturity investments	3,875	4,532	5,037
Changes in operating assets and liabilities:
Accounts receivable	(22,260)	(1,762)	(11,963)
Unbilled receivables and retentions	(1,543)	(6,427)	375
Inventories	1,928	11,285	11,862
Income tax receivable		6,584	5,193
Prepaid expenses and other assets	517	(339)	157
Accounts payable	(2,705)	5,337	(2,238)
Other liabilities	1,521	3,717	(1,045)
Net cash provided by operating activities	551	39,413	34,005
Investing activities
Acquisition of property and equipment	(6,829)	(5,279)	(7,143)
Equity method investment	(295)	(395)	(105)
Redemptions of held-to-maturity investments	84,433	69,387	75,022
Purchases of held-to-maturity investments	(94,954)	(97,464)	(56,946)
Acquisitions of intangible assets		(150)	(750)
Proceeds from the sale of property and equipment	80
Sales of available-for-sale investments	987	10,081	360
Net cash (used in) provided by investing activities	(16,578)	(23,820)	10,438
Financing activities
Excess tax benefit from stock-based compensation	39	162	648
Principal payments of capital lease obligations	(472)
Purchase and retirement of common stock	(3,756)
Tax withholding payment related to net settlement of equity awards	(29)	(36)	(163)
Exercise of stock options	1,122	722	6,709
Net cash (used in) provided by financing activities	(3,096)	848	7,194
Net (decrease) increase in cash and cash equivalents	(19,123)	16,441	51,637
Cash and cash equivalents at beginning of year	143,410	126,969	75,332
Cash and cash equivalents at end of year	124,287	143,410	126,969
Cash paid during the year for:
Income taxes	1,576	700	2,556
Non-cash activities
Unrealized change in fair value of long-term investments recorded in accumulated other comprehensive income (loss), net of tax expense (benefit) of $18, $(730) and $295 for the fiscal years ended April 30, 2016, April 30, 2015 and April 30, 2014, respectively	27	(1,095)	$ 442
Reclassification from share based liability compensation to equity	228
Forfeiture of vested stock-based compensation	86	23
Acquisitions of property and equipment financed with capital lease obligations	932
Acquisitions of property and equipment included in accounts payable	$ 1,174
Accrued acquisition of intangible assets		$ 250