Annual report pursuant to Section 13 and 15(d)

Commitments and contingencies - Narrative (Details)

v3.19.3
Commitments and contingencies - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]      
Performance bond commitments $ 36.8    
Operating lease expense 101.7 $ 77.0 $ 80.6
Operating sublease income 0.9    
Sublease income, payments to be received, 2020 $ 0.5    
Percentage of employees covered by collective bargaining agreements 8.00%    
Loss contingency, maximum potential loss $ 31.0