Segments - Net sales by major geographic area (Details) $ in Thousands	3 Months Ended		8 Months Ended	9 Months Ended
	Jan. 31, 2020 USD ($) $ / $	Jan. 31, 2019 USD ($) $ / $	Dec. 31, 2018 $ / $	Jan. 31, 2020 USD ($) $ / $	Jan. 31, 2019 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 761,352	$ 723,902		$ 2,470,457	$ 2,335,883
Average exchange rates | $ / $	0.7600	0.7491	0.7609	0.7555
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 661,491	$ 624,672		$ 2,136,968	2,021,750
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net sales	$ 99,861	$ 99,230		$ 333,489	$ 314,133