Accumulated Other Comprehensive Loss, Reclassification out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
Jul. 31, 2020	Jul. 31, 2019
Amortization from Accumulated Other Comprehensive Loss [Abstract]
Pension expense	$ (2,562)	$ (2,420)
Reclassification out of Accumulated Other Comprehensive Loss [Member]
Amortization from Accumulated Other Comprehensive Loss [Abstract]
Pension expense	$ 1,900	$ 1,300

Amount of net periodic benefit cost (credit) for defined benefit plan.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration