Business and summary of significant accounting policies - Description of Business (Details)
|12 Months Ended|
Sep. 30, 2018
|Organization, Consolidation and Presentation of Financial Statements [Abstract]|
|Number of business segments||3|
Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.
No definition available.