Goodwill and Intangible Assets - Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Intangible assets
Amortization expense	$ 43,675	$ 37,548	$ 31,957
Depreciation and amortization expense
Intangible assets
Amortization expense	$ 43,675	$ 37,548	$ 31,957