Segments - Net sales by major geographic area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 751,191	$ 761,352	$ 2,366,620	$ 2,470,457
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	637,568	661,491	2,001,020	2,136,968
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 113,623	$ 99,861	$ 365,600	$ 333,489