Goodwill and Intangible Assets - Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Intangible assets
Amortization expense	$ 41,455	$ 43,675	$ 37,548
Depreciation and amortization expense
Intangible assets
Amortization expense	$ 41,500	$ 43,700	$ 37,500