Fee Revenue - Schedule of Disaggregation of Fee Revenue by Industry (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 437,789	$ 504,177	$ 784,672	$ 1,000,375
Industrial
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 119,380	$ 141,066	$ 214,691	$ 279,378
Fee Revenue, Percentage	27.40%	28.60%	27.60%	28.60%
Financial Services
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 82,918	$ 85,188	$ 148,645	$ 171,400
Fee Revenue, Percentage	19.00%	17.30%	19.10%	17.50%
Life Sciences/Healthcare
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 83,413	$ 89,085	$ 148,863	$ 171,350
Fee Revenue, Percentage	19.20%	18.10%	19.10%	17.50%
Consumer Goods
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 60,737	$ 75,712	$ 105,515	$ 147,410
Fee Revenue, Percentage	13.90%	15.40%	13.50%	15.10%
Technology
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 64,691	$ 70,499	$ 114,015	$ 141,302
Fee Revenue, Percentage	14.90%	14.30%	14.60%	14.50%
Education/Non-Profit/General
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 24,300	$ 30,839	$ 47,807	$ 66,098
Fee Revenue, Percentage	5.60%	6.30%	6.10%	6.80%
Fee Revenue
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 435,439	$ 492,389	$ 779,536	$ 976,938
Fee Revenue, Percentage	100.00%	100.00%	100.00%	100.00%