XML 84 R69.htm IDEA: XBRL DOCUMENT v3.8.0.1
Employee Benefit Plans - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2015
Retirement Benefits [Abstract]      
Eligible employees contribution to 401(k) plan (up to 25%) 25.00%    
Employer contributions into 401(k) plans $ 8.4 $ 7.3 $ 7.1
Employee incentive plans expenses $ 41.6 $ 40.0 $ 20.3