Long-Term Debt - Asset-Based Lending Facility (Details) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2018	Oct. 31, 2017
Long-term debt
Net borrowings	$ 623,117	$ 352,567
ABL Facility
Long-term debt
Maximum amount under the facility	$ 345,000
Borrowing interest rate (as a percent)	3.93%
Available borrowings under the facility	$ 181,700
Net borrowings	153,500
ABL Facility | Swing-line
Long-term debt
Maximum amount under the facility	$ 34,500