Pension and Other Postretirement Benefits (Textual) (Details) $ in Millions	Apr. 30, 2018 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to benefit plans in 2019	$ 5
Estimated amount of prior service cost that will be amortized from accumulated other comprehensive loss into pension expense in 2019	(1)
Estimated amount of net actuarial loss that will be amortized from accumulated other comprehensive loss into pension expense in 2019	19
Medical and Life Insurance Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to benefit plans in 2019	3
Estimated amount of prior service cost that will be amortized from accumulated other comprehensive loss into pension expense in 2019	3
Estimated amount of net actuarial loss that will be amortized from accumulated other comprehensive loss into pension expense in 2019	$ 1