Business, Basis of Presentation and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Apr. 30, 2018
Adoption of new accounting pronouncement
Trade accounts and notes receivable	$ 479,327		$ 346,450
Other accrued expenses and current liabilities	66,727		$ 45,146
Other accrued expenses and liabilities	5,325	$ 2,170
Debt issuance costs	7,933	3,283
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