CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Operating activities
Net income	$ 19,852	$ 12,457	$ 8,966
Loss from discontinued operations, net of tax	(2,508)	(4,154)	(6,427)
Net income from continuing operations	22,360	16,611	15,393
Adjustments to reconcile net income (loss) to cash provided by (used in) operating activities:
Depreciation and amortization	5,982	5,054	3,855
Loss from equity method investments	1,283	119	138
Impairment of available-for-sale securities			2,186
Impairment of long-lived assets	255	46
Provision for doubtful accounts	977	48	18
Impairment of intangible assets and goodwill	1,021
(Gains) losses on foreign currency transactions	(87)	284	63
Loss on sale of equity securities			219
Deferred income taxes	3,835	(52)	(2,912)
Gain on business acquisition		(584)
Stock-based compensation	4,956	3,392	4,002
Tax benefit from exercise of stock options			161
Excess tax benefit from stock-based compensation			(39)
Loss (Gain) on disposition of property and equipment	20	44
Amortization of held-to-maturity investments	1,424	2,382	3,875
Changes in operating assets and liabilities:
Accounts receivable	11,211	(19,608)	(20,645)
Unbilled receivables and retentions	903	4,667	(1,555)
Inventories	2,268	(19,225)	480
Prepaid expenses and other assets	419	(1,484)	439
Accounts payable	5,736	545	(2,851)
Other liabilities	7,872	(233)	3,221
Net cash provided by (used in) operating activities of continuing operations	70,436	(7,994)	6,047
Investing activities
Acquisition of property and equipment	(9,563)	(9,017)	(6,121)
Equity method investments	(3,267)		(295)
Business acquisition, net of cash acquired		(430)
Redemptions of held-to-maturity investments	227,663	121,522	84,433
Purchases of held-to-maturity investments	(221,680)	(148,991)	(94,954)
Redemptions of available-for-sale investments	450	400	987
Net cash used in investing activities from continuing operations	(6,397)	(36,516)	(15,950)
Financing activities
Purchase and retirement of common stock			(3,756)
Principal payments of capital lease obligations	(288)	(390)	(472)
Excess tax benefit from stock-based compensation			39
Tax withholding payment related to net settlement of equity awards	(397)	(5)	(29)
Exercise of stock options	2,705	3,865	1,122
Net cash provided by (used in) financing activities from continuing operations	2,020	3,470	(3,096)
Discontinued operations
Operating activities of discontinued operations	(1,227)	(2,505)	(5,496)
Investing activities of discontinued operations	(1,219)	(838)	(628)
Net cash provided by (used in) discontinued operations	(2,446)	(3,343)	(6,124)
Net increase (decrease) in cash and cash equivalents	63,613	(44,383)	(19,123)
Cash and cash equivalents at beginning of period	79,904	124,287	143,410
Cash and cash equivalents at end of period	143,517	79,904	124,287
Cash paid, net during the period for:
Income taxes	1,813	1,804	1,576
Non-cash activities
Unrealized gain on investments, net of deferred tax expense of $29 and $6, respectively	70	74	27
Reclassification from share-based liability compensation to equity	384	307	228
Forfeiture of vested stock-based compensation			86
Acquisitions of property and equipment financed with capital lease obligations			932
Change in foreign currency translation adjustments	36
Acquisitions of property and equipment included in accounts payable	$ 379	$ 724	$ 1,045