Deferred Compensation And Retirement Plans (Weighted-Average Assumptions Used In Calculating The Benefit Obligations) (Detail)	12 Months Ended
Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Discount rate, beginning of year	3.57%	3.18%	3.28%
Discount rate, end of year	3.93%	3.57%	3.18%
Rate of compensation increase	0.00%	0.00%	0.00%
Expected long-term rates of return on plan assets	6.25%	6.50%	6.50%
Medical and Life Insurance plan \| Hay Group
Defined Benefit Plan Disclosure [Line Items]
Discount rate, beginning of year	3.75%	3.36%	4.10%
Discount rate, end of year	3.94%	3.75%	3.36%
Healthcare care cost trend rate	7.00%	7.00%	7.00%

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- 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.

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- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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