Business, Basis of Presentation and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Apr. 30, 2018
Adoption of new accounting pronouncement
Trade accounts and notes receivable	$ 474,394		$ 346,450
Other accrued expenses and current liabilities	60,640		$ 45,146
Other accrued expenses and liabilities	2,219	$ 14,026
Debt issuance costs	7,933	$ 3,308
ASU 2014-09
Adoption of new accounting pronouncement
Trade accounts and notes receivable	3,600
Other accrued expenses and current liabilities	3,600
ASU 2016-15
Adoption of new accounting pronouncement
Other accrued expenses and liabilities	2,700
Debt issuance costs	$ 2,700