Pension and Other Postretirement Benefits (Change in Fair Value of Pension Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
Apr. 30, 2019	Apr. 30, 2018
Change in fair value of pension plan Assets
Beginning balance	$ 780
Ending balance	754	$ 780
Pension Benefits [Member]
Change in fair value of pension plan Assets
Beginning balance	780	623
Actual return on assets	34	53
Retiree contributions	0	0
Company contributions	21	155
Benefits paid	(81)	(51)
Ending balance	754	780
Medical and Life Insurance Benefits [Member]
Change in fair value of pension plan Assets
Beginning balance	0	0
Actual return on assets	0	0
Retiree contributions	1	1
Company contributions	3	3
Benefits paid	(4)	(4)
Ending balance	$ 0	$ 0

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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- Definition

Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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- Definition

Amount of contributions received by defined benefit plan from participant which increases plan assets.

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