Goodwill and Intangible Assets - Amortization (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Intangible assets
Amortization expense	$ 10,481	$ 11,851	$ 31,527	$ 32,084
Depreciation and amortization expense
Intangible assets
Amortization expense	$ 10,500	$ 11,900	$ 31,500	$ 32,100