Fee Revenue - Schedule of Disaggregation of Fee Revenue by Industry (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2021	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Disaggregation Of Revenue [Line Items]
Fee Revenue									$ 1,819,946	$ 1,977,330	$ 1,973,862
Industrial
Disaggregation Of Revenue [Line Items]
Fee Revenue									$ 490,863	$ 556,189	$ 557,284
Fee Revenue, Percentage									27.10%	28.80%	28.90%
Life Sciences/ Healthcare
Disaggregation Of Revenue [Line Items]
Fee Revenue									$ 355,668	$ 343,955	$ 322,574
Fee Revenue, Percentage									19.70%	17.80%	16.70%
Financial Services
Disaggregation Of Revenue [Line Items]
Fee Revenue									$ 331,976	$ 334,433	$ 348,460
Fee Revenue, Percentage									18.30%	17.30%	18.10%
Consumer Goods
Disaggregation Of Revenue [Line Items]
Fee Revenue									$ 239,457	$ 285,927	$ 295,900
Fee Revenue, Percentage									13.20%	14.80%	15.40%
Technology
Disaggregation Of Revenue [Line Items]
Fee Revenue									$ 275,510	$ 285,562	$ 261,176
Fee Revenue, Percentage									15.20%	14.80%	13.60%
Education/Non-Profit/General
Disaggregation Of Revenue [Line Items]
Fee Revenue									$ 116,573	$ 126,666	$ 140,639
Fee Revenue, Percentage									6.50%	6.50%	7.30%
Fee Revenue
Disaggregation Of Revenue [Line Items]
Fee Revenue	$ 555,151	$ 475,360	$ 435,439	$ 344,097	$ 440,469	$ 515,325	$ 492,389	$ 484,549	$ 1,810,047	$ 1,932,732	$ 1,926,033
Fee Revenue, Percentage									100.00%	100.00%	100.00%