Revenue Recognition (Deferred Revenue) (Details) - POM - USD ($) $ in Thousands	9 Months Ended
Jan. 31, 2019	Jan. 31, 2018
Deferred Revenue
Movement in Deferred Revenue [Roll Forward]
Balance, beginning of the period	$ 218,274	$ 211,223
Amounts deferred	27,711	29,023
Amounts recognized on previous deferrals	(90,439)	(86,347)
Balance, end of the period	155,546	153,899
Deferred Wages
Movement in Deferred Revenue [Roll Forward]
Balance, beginning of the period	32,683	31,344
Amounts deferred	1,773	2,649
Amounts recognized on previous deferrals	(13,569)	(12,496)
Balance, end of the period	$ 20,887	$ 21,497

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

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