Pension and Other Postretirement Benefits (Textual) (Details) $ in Millions	12 Months Ended
	Apr. 30, 2016 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to benefit plans in 2017	$ 30
Estimated amount of prior service cost that will be amortized from accumulated other comprehensive loss into pension expense in 2017	1
Estimated amount of net actuarial loss that will be amortized from accumulated other comprehensive loss into pension expense in 2017	25
Medical and Life Insurance Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to benefit plans in 2017	3
Estimated amount of prior service cost that will be amortized from accumulated other comprehensive loss into pension expense in 2017	3
Estimated amount of net actuarial loss that will be amortized from accumulated other comprehensive loss into pension expense in 2017	$ 1