Long-Term Debt - Asset-Based Lending Facility (Details) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2019	Jan. 31, 2018
Long-term debt
Net borrowings	$ 886,896	$ 493,739
ABL Facility
Long-term debt
Maximum amount under the facility	$ 345,000
Borrowing interest rate (as a percent)	4.01%
Available borrowings under the facility	$ 197,300
Net borrowings	137,900
ABL Facility | Swing-line
Long-term debt
Maximum amount under the facility	$ 34,500