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Retirement Plans, Recent Plan Curtailments (Details) | 12 Months Ended
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Apr. 30, 2018
Minimum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Employee retirement age limit under retirement plans | 60 years
Maximum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Employee retirement age limit under retirement plans | 65 years
Supplemental Executive Retirement Plan [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Term of supplemental retirement benefits | 10 years

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- Definition Refers to the employee retirement age limit under retirement plans based on length of service and compensation, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | jwa_EmployeeRetirementAgeLimitUnderRetirementPlans
Namespace Prefix: | jwa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The period of time subsequent to termination of employment during which the company provides for the payment of supplemental retirement benefits for certain officers and senior management, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | jwa_TermOfSupplementalRetirementBenefits
Namespace Prefix: | jwa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |