Annual report pursuant to Section 13 and 15(d)

Fee Revenue Classified by Country (Detail)

v3.7.0.1
Fee Revenue Classified by Country (Detail) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Apr. 30, 2017
Jan. 31, 2017
Oct. 31, 2016
Jul. 31, 2016
Apr. 30, 2016
Jan. 31, 2016
Oct. 31, 2015
Jul. 31, 2015
Apr. 30, 2017
Apr. 30, 2016
Apr. 30, 2015
Segment Reporting Information [Line Items]                      
Fee revenue $ 406,065 $ 381,918 $ 401,917 $ 375,621 $ 399,960 $ 344,158 $ 280,600 $ 267,394 $ 1,565,521 $ 1,292,112 $ 1,028,152
UNITED STATES                      
Segment Reporting Information [Line Items]                      
Fee revenue                 728,871 669,585 557,024
Other Countries                      
Segment Reporting Information [Line Items]                      
Fee revenue                 $ 836,650 $ 622,527 $ 471,128