Employee and Retiree Benefits (Narrative) (Details)	1 Months Ended						9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012	May 27, 2017
Compensation and Retirement Disclosure [Abstract]
Postretirement health care benefits age requirement before distribution occurs							55 years
Postretirement health care benefits continuous service requirement							15 years
Dollar cap liability reduction		10.00%	10.00%	10.00%	10.00%	10.00%
Postretirement health care retiree age requirement	65 years	65 years