Long-Term Debt - Acquisition Debt (Details) - USD ($) $ in Thousands						3 Months Ended	9 Months Ended
	Jan. 31, 2018	Jun. 07, 2017	Sep. 27, 2016	Jun. 01, 2016	Apr. 01, 2014	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Long-term debt
Repayment of amounts outstanding under credit facility							$ 597,092	$ 817,598
Net amount of debt issued							577,616	481,225
Cash paid for interest							21,192	20,038
Write-off of debt discount and deferred financing fees						$ 211	$ 74	7,103
Term Loan Facilities, April 1, 2014
Long-term debt
Face amount of debt					$ 550,000
First Lien Term Loan due 2021
Long-term debt
Net amount of debt issued					388,100
Original issue discount					2,000
Loan repayment		$ 477,600
Second Lien Term Loan due 2022
Long-term debt
Net amount of debt issued					158,400
Original issue discount					$ 1,600
Loan repayment				$ 160,000				160,000
Write-off of debt discount and deferred financing fees				$ 5,400
Incremental First Lien Term Commitments Amendment
Long-term debt
Face amount of debt			$ 481,200
Reduction to interest rate margin at each pricing level (as a percent)			(0.25%)
Loan repayment			$ 381,200
Write-off of debt discount and deferred financing fees								1,500
Incremental First Lien Term Commitments Amendment | LIBOR
Long-term debt
Variable rate floor (as a percent)			1.00%
Margin added to variable rate (as a percent)			3.50%
Second amendment to First Lien Credit Agreement
Long-term debt
Face amount of debt		$ 577,600
Borrowing interest rate (as a percent)	4.77%						4.77%
Reduction to interest rate margin at each pricing level (as a percent)		(0.50%)
Loan repayment							$ 477,616	$ 381,225
Write-off of debt discount and deferred financing fees							$ 100
Second amendment to First Lien Credit Agreement | LIBOR
Long-term debt
Variable rate floor (as a percent)		1.00%
Margin added to variable rate (as a percent)		3.00%
ABL Facility
Long-term debt
Borrowing interest rate (as a percent)	4.75%						4.75%
Loan repayment	$ 94,000