Annual report pursuant to Section 13 and 15(d)

Fee Revenue - Schedule of Disaggregation of Fee Revenue by Industry (Detail)

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Fee Revenue - Schedule of Disaggregation of Fee Revenue by Industry (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Apr. 30, 2019
Jan. 31, 2019
Oct. 31, 2018
Jul. 31, 2018
Apr. 30, 2018
Jan. 31, 2018
Oct. 31, 2017
Jul. 31, 2017
Apr. 30, 2019
Apr. 30, 2018
Apr. 30, 2017
Disaggregation Of Revenue [Line Items]                      
Fee Revenue                 $ 1,973,862 $ 1,819,519 $ 1,621,669
Industrial                      
Disaggregation Of Revenue [Line Items]                      
Fee Revenue                 $ 561,029 $ 530,547 $ 459,732
Fee Revenue, Percentage                 29.10% 30.00% 29.40%
Financial Services                      
Disaggregation Of Revenue [Line Items]                      
Fee Revenue                 $ 349,968 $ 305,047 $ 257,671
Fee Revenue, Percentage                 18.20% 17.30% 16.40%
Life Sciences/ Healthcare                      
Disaggregation Of Revenue [Line Items]                      
Fee Revenue                 $ 323,091 $ 294,999 $ 273,493
Fee Revenue, Percentage                 16.80% 16.70% 17.50%
Consumer Goods                      
Disaggregation Of Revenue [Line Items]                      
Fee Revenue                 $ 297,676 $ 276,979 $ 263,671
Fee Revenue, Percentage                 15.50% 15.70% 16.80%
Technology                      
Disaggregation Of Revenue [Line Items]                      
Fee Revenue                 $ 260,918 $ 226,142 $ 198,867
Fee Revenue, Percentage                 13.50% 12.80% 12.70%
Education/Non-Profit                      
Disaggregation Of Revenue [Line Items]                      
Fee Revenue                 $ 122,524 $ 120,809 $ 99,978
Fee Revenue, Percentage                 6.30% 6.80% 6.40%
General                      
Disaggregation Of Revenue [Line Items]                      
Fee Revenue                 $ 10,827 $ 12,694 $ 12,109
Fee Revenue, Percentage                 0.60% 0.70% 0.80%
Fee Revenue                      
Disaggregation Of Revenue [Line Items]                      
Fee Revenue $ 490,756 $ 474,504 $ 495,205 $ 465,568 $ 475,364 $ 447,581 $ 443,018 $ 401,254 $ 1,926,033 $ 1,767,217 $ 1,565,521
Fee Revenue, Percentage                 100.00% 100.00% 100.00%