Stock-Based Compensation Plans - Schedule of Fair Value at the Date of Grant (Detail)	12 Months Ended
	Sep. 30, 2018 shares
Fiscal 2016 (2016 - 2018) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum Shares	11,910
Target Shares	59,548
Maximum Shares	119,096
Fiscal 2017 (2017 - 2019) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum Shares	9,352
Target Shares	46,758
Maximum Shares	93,516