Stock-Based Compensation - Summary of Restricted Share and Performance-Based Stock Award Activity (Details) - $ / shares	9 Months Ended	12 Months Ended
	Jun. 30, 2020	Sep. 30, 2019
Restricted Shares
Common Shares
Shares, beginning of fiscal year (in shares)	190,805	163,287
Granted (in shares)	146,466	106,753
Vested (in shares)	(84,096)	(76,210)
Forfeited (in shares)	(3,742)	(3,025)
Canceled (in shares)	0	0
Shares, end of period (in shares)	249,433	190,805
Vested, but not issuable at end of period (in shares)	62,992	50,770
Weighted-Average Grant Date Fair Value
Shares, beginning of fiscal year (in dollars per share)	$ 37.20	$ 37.86
Granted (in dollars per share)	30.78	37.27
Vested (in dollars per share)	38.61	38.64
Forfeited (in dollars per share)	36.48	38.67
Canceled (in dollars per share)	0	0
Shares, end of period (in dollars per share)	32.96	37.20
Vested, but not issuable at end of period (in dollars per share)	$ 33.98	$ 33.88
Performance Shares
Common Shares
Shares, beginning of fiscal year (in shares)	173,332	175,196
Granted (in shares)	(44,629)	60,583
Vested (in shares)	(54,861)	(59,937)
Forfeited (in shares)	(4,407)	(2,510)
Canceled (in shares)	0	0
Shares, end of period (in shares)	69,435	173,332
Vested, but not issuable at end of period (in shares)	5,612	5,612
Weighted-Average Grant Date Fair Value
Shares, beginning of fiscal year (in dollars per share)	$ 38.50	$ 36.29
Granted (in dollars per share)	(57.47)	32.77
Vested (in dollars per share)	39.43	30.79
Forfeited (in dollars per share)	37.97	39.25
Canceled (in dollars per share)	0	0
Shares, end of period (in dollars per share)	35.12	38.50
Vested, but not issuable at end of period (in dollars per share)	$ 18.00	$ 18.00