Annual report pursuant to Section 13 and 15(d)

Earnings per share - Narrative (Details)

v3.8.0.1
Earnings per share - Narrative (Details) - shares
12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2015
Unvested restricted stock units      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Awards excluded from the calculation of diluted earnings per share (in shares) 9,000 21,000 15,000