Segments - Additional Information (Detail) - Segment	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Segment Reporting Information [Line Items]
Number of business segments	7
Number of line of business	4
Geographic Concentration Risk | Sales Revenue, Net [Member] | UNITED STATES | Minimum
Segment Reporting Information [Line Items]
Concentration risk percentage	10.00%	10.00%	10.00%
Geographic Concentration Risk | Sales Revenue, Net [Member] | United Kingdom | Minimum
Segment Reporting Information [Line Items]
Concentration risk percentage	10.00%	10.00%	10.00%
Geographic Concentration Risk | Long-Lived Assets | UNITED STATES | Minimum
Segment Reporting Information [Line Items]
Concentration risk percentage	10.00%	10.00%	10.00%
Geographic Concentration Risk | Long-Lived Assets | United Kingdom | Minimum
Segment Reporting Information [Line Items]
Concentration risk percentage	10.00%	10.00%	10.00%