Annual report pursuant to Section 13 and 15(d)

Fee Revenue - Additional Information (Detail)

Fee Revenue - Additional Information (Detail)
$ in Millions
12 Months Ended
Apr. 30, 2019
USD ($)
Revenue From Contract With Customer [Abstract]  
Contract liabilities, revenue recognized $ 97.0
Revenue recognized, remaining performance obligation $ 539.5
Revenue, practical expedient, initial application and transition, completed contract, same reporting period true
Revenue, remaining performance obligation, optional exemption, performance obligation true