Revenue Recognition (Changes in Balances of Deferred Revenue and Wages) (Details) - POM - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2020	Apr. 30, 2019
Deferred Revenue
Movement in Deferred Revenue [Roll Forward]
Balance, beginning of the year	$ 212,511	$ 218,274
Amounts deferred	95,032	120,163
Amounts recognized on previous deferrals	(123,858)	(125,926)
Balance, end of the year	183,685	212,511
Deferred Wages
Movement in Deferred Revenue [Roll Forward]
Balance, beginning of the year	27,306	32,683
Amounts deferred	10,708	13,336
Amounts recognized on previous deferrals	(16,396)	(18,713)
Balance, end of the year	$ 21,618	$ 27,306

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118944033&loc=SL49130531-203044

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130549-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118944033&loc=SL49130532-203044

Name:	us-gaap_ContractWithCustomerLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant