Basis of Presentation, Business and Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Selling, general and administrative expenses
Property and equipment
Impairment losses related to land and buildings held for sale	$ 485	$ 373	$ 173
Buildings | Minimum
Property and equipment
Estimated useful life	25 years
Buildings | Maximum
Property and equipment
Estimated useful life	39 years
Leasehold improvements | Minimum
Property and equipment
Estimated useful life	1 year
Leasehold improvements | Maximum
Property and equipment
Estimated useful life	15 years
Furniture, fixtures and automobiles | Minimum
Property and equipment
Estimated useful life	3 years
Furniture, fixtures and automobiles | Maximum
Property and equipment
Estimated useful life	5 years
Warehouse and delivery equipment | Minimum
Property and equipment
Estimated useful life	4 years
Warehouse and delivery equipment | Maximum
Property and equipment
Estimated useful life	5 years
Assets held under capital lease | Minimum
Property and equipment
Estimated useful life	2 years
Assets held under capital lease | Maximum
Property and equipment
Estimated useful life	11 years