Fee Revenue - Schedule of Disaggregation of Fee Revenue by Industry (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 477,880	$ 527,979	$ 1,262,552	$ 1,528,354
Industrial
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 131,959	$ 149,067	$ 346,650	$ 428,445
Fee Revenue, Percentage	27.80%	28.90%	27.60%	28.70%
Financial Services
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 84,078	$ 84,778	$ 232,723	$ 256,178
Fee Revenue, Percentage	17.70%	16.50%	18.50%	17.20%
Life Sciences/Healthcare
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 92,588	$ 89,217	$ 241,451	$ 260,567
Fee Revenue, Percentage	19.50%	17.30%	19.30%	17.50%
Consumer Goods
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 63,325	$ 78,600	$ 168,840	$ 226,010
Fee Revenue, Percentage	13.30%	15.30%	13.50%	15.10%
Technology
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 74,774	$ 79,870	$ 188,789	$ 221,172
Fee Revenue, Percentage	15.70%	15.50%	15.00%	14.80%
Education/Non-Profit/General
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 28,636	$ 33,793	$ 76,443	$ 99,891
Fee Revenue, Percentage	6.00%	6.50%	6.10%	6.70%
Fee Revenue
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 475,360	$ 515,325	$ 1,254,896	$ 1,492,263
Fee Revenue, Percentage	100.00%	100.00%	100.00%	100.00%