Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	$ 1,020,213	$ 1,178,996	$ 933,624	$ 1,181,347
Other comprehensive income (loss) before reclassifications	39,687	5,561	68,703	7,358
Amounts reclassified from Accumulated Other Comprehensive Loss	2,426	1,125	7,265	3,040
Total Other Comprehensive (Loss) Income	42,113	6,686	75,968	10,398
Balance	1,063,802	1,197,235	1,063,802	1,197,235
Accumulated Other Comprehensive Loss [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(541,642)	(505,026)	(575,497)	(508,738)
Balance	(499,529)	(498,340)	(499,529)	(498,340)
Foreign Currency Translation [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(305,476)	(309,327)	(340,703)	(312,107)
Other comprehensive income (loss) before reclassifications	48,305	7,895	83,532	10,675
Amounts reclassified from Accumulated Other Comprehensive Loss	0	0	0	0
Total Other Comprehensive (Loss) Income	48,305	7,895	83,532	10,675
Balance	(257,171)	(301,432)	(257,171)	(301,432)
Unamortized Retirement Costs [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(230,182)	(194,465)	(227,920)	(196,057)
Other comprehensive income (loss) before reclassifications	(8,237)	(2,063)	(13,527)	(2,893)
Amounts reclassified from Accumulated Other Comprehensive Loss	1,463	1,247	4,491	3,669
Total Other Comprehensive (Loss) Income	(6,774)	(816)	(9,036)	776
Balance	(236,956)	(195,281)	(236,956)	(195,281)
Interest Rate Swaps [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(5,984)	(1,234)	(6,874)	(574)
Other comprehensive income (loss) before reclassifications	(381)	(271)	(1,302)	(424)
Amounts reclassified from Accumulated Other Comprehensive Loss	963	(122)	2,774	(629)
Total Other Comprehensive (Loss) Income	582	(393)	1,472	(1,053)
Balance	$ (5,402)	$ (1,627)	$ (5,402)	$ (1,627)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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