Basis of Presentation - Narrative (Details) - USD ($)	3 Months Ended				6 Months Ended
	Oct. 31, 2021	Jul. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Operating income	$ 5,533,000		$ 36,044,000		$ 11,989,000	$ 62,270,000
Net income	$ 2,030,000	$ 2,981,000	$ 23,122,000	$ 16,059,000	$ 5,011,000	$ 39,181,000
Earnings per share, basic (in usd per share)	$ 0.12		$ 1.36		$ 0.30	$ 2.31
Earnings per share, diluted (in usd per share)	$ 0.12		$ 1.36		$ 0.30	$ 2.30
Impairment charges related to goodwill	$ 0		$ 0		$ 0	$ 0
Revision of Prior Period, Change in Accounting Principle, Adjustment
Finite-Lived Intangible Assets [Line Items]
Operating income	3,000,000
Net income	$ 2,200,000
Earnings per share, basic (in usd per share)	$ 0.13
Earnings per share, diluted (in usd per share)	$ 0.13
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Impairment charges related to other intangible assets	$ 0		$ 0		$ 0	$ 0
Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets estimated useful lives					6 years