Annual report pursuant to Section 13 and 15(d)

Employee benefit plans and deferred compensation - Narrative (Details)

v3.5.0.2
Employee benefit plans and deferred compensation - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]      
Employer contribution to 401(k) plans $ 6.0 $ 4.7 $ 4.3
Percentage of liabilities that can be met plan assets 96.00%    
Investments in mutual funds within the rabbi trust $ 11.8