Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2017	Oct. 31, 2016
Statement of Cash Flows [Abstract]
Payments to Acquire Other Investments	$ 25,000	$ 50,500
OPERATING ACTIVITIES
Net income	42,036	39,298
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	10,977	8,873
Net loss on disposal of property, plant and equipment	84	174
Stock-based compensation expense	1,609	1,649
Deferred income taxes	7,750	11,250
Pension contributions in excess of expense	(9,081)	(10,732)
Contributions of employer stock to employee benefit plan	3,554	2,926
Other non-cash items	(290)	88
Changes in operating assets and liabilities:
Customer receivables	(2,954)	(12,847)
Inventories	(4,523)	(1,942)
Prepaid expenses and other assets	(6,245)	(2,917)
Accounts payable	(2,573)	2,878
Accrued compensation and related expenses	(1,044)	(1,754)
Other accrued expenses	2,538	3,202
Net cash provided by operating activities	41,838	40,146
INVESTING ACTIVITIES
Payments to acquire property, plant and equipment	(20,660)	(10,354)
Proceeds from sales of property, plant and equipment	2	26
Proceeds from Maturities, Prepayments and Calls of Other Investments	15,500	12,500
Investment in promotional displays	(978)	(2,089)
Net cash used by investing activities	(31,136)	(50,417)
FINANCING ACTIVITIES
Payments of long-term debt	(876)	(854)
Proceeds from long-term debt	734	2,003
Proceeds from issuance of common stock	1,286	2,241
Repurchase of common stock	(23,500)	(10,443)
Notes receivable, net	0	208
Withholding of employee taxes related to stock-based compensation	(2,779)	(1,703)
Net cash used by financing activities	(25,135)	(8,548)
Net decrease in cash and cash equivalents	(14,433)	(18,819)
Cash and cash equivalents, beginning of period	176,978	174,463
Cash and cash equivalents, end of period	$ 162,545	$ 155,644