Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Cash flows from operating activities:
Net income	$ 18,410	$ 20,128	$ 127,854
Adjustments to reconcile net income to net cash provided by/(used in) operating activities:
Depreciation and amortization	53,859	52,075	50,213
(Gain)/loss on sale/disposition of assets	(454)	44	99
Provision for losses on notes and accounts receivable	1,060	991	1,546
Impairment of long-lived tangible assets		282
Goodwill impairment	10,396
Deferred income taxes	(2,795)	(8,775)	(7,840)
Change in fair value of contingent consideration	(60)	(1,640)
Stock-based compensation expense	7,992	7,815	8,590
Changes in operating assets and liabilities:
Accounts receivable	(28,997)	51,380	(40,709)
Inventories	(10,533)	(16,971)	(22,171)
Prepaid expenses and other current assets	359	514	(1,619)
Income taxes	1,780	5,848	(13,745)
Accounts payable	3,392	(20,998)	1,233
Accrued payroll and incentives	10,959	(10,754)	988
Accrued profit sharing	1,547	(11,721)	1,545
Accrued expenses and deferred revenue	(7,193)	(8,424)	21,238
Accrued warranty	(1,224)	1,915	(1,415)
Other assets	(671)	(417)	1,029
Other non-current liabilities	(377)	351	(3,260)
Net cash provided by operating activities	57,450	61,643	123,576
Cash flows from investing activities:
Acquisition of businesses, net of cash acquired	(1,772)	(23,120)	(211,069)
Refunds on machinery and equipment			2,776
Receipts from note receivable	74		65
Payments to acquire patents and software	(516)	(560)	(638)
Proceeds from sale of property and equipment	1,336	6
Payments to acquire property and equipment	(33,949)	(18,490)	(34,876)
Net cash used in investing activities	(34,827)	(42,164)	(243,742)
Cash flows from financing activities:
Proceeds from loans and notes payable	50,000	150,000	100,000
Cash paid for debt issuance costs		(158)	(525)
Payments on capital lease obligation	(741)	(646)	(558)
Payments on notes and loans payable	(81,300)	(181,300)	(56,300)
Proceeds from Economic Development Incentive Program			101
Payments to acquire treasury stock			(50,052)
Proceeds from exercise of options to acquire common stock, including employee stock purchase plan	2,222	2,213	2,442
Payment of employee withholding tax related to restricted stock units	(649)	(2,277)	(4,672)
Net cash used in financing activities	(30,468)	(32,168)	(9,564)
Net decrease in cash and cash equivalents	(7,845)	(12,689)	(129,730)
Cash and cash equivalents, beginning of period	48,860	61,549	191,279
Cash and cash equivalents, end of period	41,015	48,860	61,549
Supplemental disclosure of cash flow information Cash paid for:
Interest	9,473	10,624	7,650
Income taxes	10,567	1,387	85,216
Supplemental Disclosure of Non-cash Investing and Financing Activities:
Purchases of property and equipment included in accounts payable	565	2,406	2,474
Change in fair value of interest rate swap	1,393	1,531	1,860
Contingent consideration		100	$ 1,700
Purchases of property and equipment funded by capital lease	24,271	21,974
Capital lease obligation	24,271	$ 21,974
Changes in note receivable	$ 1,007