Goodwill and Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Jul. 31, 2019	Apr. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Total definite-lived intangible assets, Gross Carrying Amount	$ 173,436	$ 173,314
Total definite-lived intangible assets, Accumulated Amortization	(86,549)	(81,700)
Total definite-lived intangible assets, Net Carrying Amount	86,887	91,614
Indefinite-lived intangible assets, Net Carrying Amount	226	226
Total Intangible assets, Gross Carrying Amount	173,662	173,540
Total Intangible assets, Net Carrying Amount	87,113	91,840
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Total definite-lived intangible assets, Gross Carrying Amount	92,560	92,560
Total definite-lived intangible assets, Accumulated Amortization	(44,478)	(41,643)
Total definite-lived intangible assets, Net Carrying Amount	48,082	50,917
Developed technology
Finite-Lived Intangible Assets [Line Items]
Total definite-lived intangible assets, Gross Carrying Amount	21,230	21,230
Total definite-lived intangible assets, Accumulated Amortization	(10,947)	(10,428)
Total definite-lived intangible assets, Net Carrying Amount	10,283	10,802
Patents, trademarks, and trade names
Finite-Lived Intangible Assets [Line Items]
Total definite-lived intangible assets, Gross Carrying Amount	57,659	57,477
Total definite-lived intangible assets, Accumulated Amortization	(29,974)	(28,479)
Total definite-lived intangible assets, Net Carrying Amount	27,685	28,998
Backlog
Finite-Lived Intangible Assets [Line Items]
Total definite-lived intangible assets, Gross Carrying Amount	1,150	1,150
Total definite-lived intangible assets, Accumulated Amortization	(1,150)	(1,150)
Definite-lived intangible assets excluding patents in progress
Finite-Lived Intangible Assets [Line Items]
Total definite-lived intangible assets, Gross Carrying Amount	172,599	172,417
Total definite-lived intangible assets, Accumulated Amortization	(86,549)	(81,700)
Total definite-lived intangible assets, Net Carrying Amount	86,050	90,717
Patents in progress
Finite-Lived Intangible Assets [Line Items]
Total definite-lived intangible assets, Gross Carrying Amount	837	897
Total definite-lived intangible assets, Net Carrying Amount	$ 837	$ 897