Annual report pursuant to Section 13 and 15(d)

Significant Accounting Policies - Stripping Costs (Details)

v3.22.2.2
Significant Accounting Policies - Stripping Costs (Details) - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2020
Accounting Policies [Abstract]      
Capitalized costs, pre-production stripping costs $ 3.9 $ 2.7  
Production costs, period cost $ 1.7 $ 1.8 $ 1.3