Stock-Based Compensation - Restricted Stock Plan and Performance Shares (Details) - USD ($) $ / shares in Units, $ in Thousands | 3 Months Ended | 6 Months Ended |
Mar. 31, 2022 | Mar. 31, 2021 | Mar. 31, 2022 | Mar. 31, 2021 |
Restricted Stock | 2009 Restricted Stock Plan | | | | |
Restricted stock plan activity, number of shares | | | | |
Unvested and deferred at beginning of the period (in shares) | | | 142,269 | |
Granted (in shares) | | | 31,704 | |
Forfeited / Canceled (in shares) | | | (6,522) | |
Vested and deferred (in shares) | | | (44,615) | |
Unvested and deferred at end of the period (in shares) | 122,836 | | 122,836 | |
Expected to vest (in shares) | 122,836 | | 122,836 | |
Restricted stock plan activity, Weighted Average Fair Value at Grant Date | | | | |
Unvested and deferred at beginning of the period (in dollars per share) | | | $ 26.78 | |
Granted (in dollars per share) | | | 44.07 | |
Forfeited / Canceled (in dollars per share) | | | 28.79 | |
Vested and deferred (in dollars per share) | | | 29.88 | |
Unvested and deferred at end of the period (in dollars per share) | $ 30.01 | | 30.01 | |
Expected to vest (in dollars per share) | $ 30.01 | | $ 30.01 | |
Deferred Restricted Stock plan activity, number of shares | | | | |
Vested (in shares) | | | 44,615 | |
Deferred Restricted Stock plan activity, Weighted Average Fair Value at Grant Date | | | | |
Vested and deferred (in dollars per share) | | | $ 29.88 | |
Restricted stock plan activity, other disclosures | | | | |
Compensation expense | $ 352 | $ 524 | $ 744 | $ 1,019 |
Remaining unrecognized compensation expense | $ 1,949 | | $ 1,949 | |
Weighted average period for recognition | | | 1 year 3 months 18 days | |
Restricted Stock | 2009 Restricted Stock Plan | Employee | | | | |
Restricted stock plan activity, other disclosures | | | | |
Repurchase of stock from employees (in shares) | | | 13,798 | |
Average purchase price (in dollars per share) | $ 42.52 | | $ 42.52 | |
Restricted Stock | 2016 Restricted Stock Plan | | | | |
Restricted stock plan activity, other disclosures | | | | |
Compensation expense | | | $ 84 | 104 |
Deferred Restricted Stock | 2016 Restricted Stock Plan | | | | |
Restricted stock plan activity, number of shares | | | | |
Vested and deferred (in shares) | | | (20,500) | |
Restricted stock plan activity, Weighted Average Fair Value at Grant Date | | | | |
Vested and deferred (in dollars per share) | | | $ 29.23 | |
Deferred Restricted Stock plan activity, number of shares | | | | |
Outstanding at beginning of period (in shares) | | | 7,398 | |
Granted (in shares) | | | 3,801 | |
Vested and deferred (in shares) | | | (7,398) | |
Outstanding at end of period (in shares) | 3,801 | | 3,801 | |
Vested (in shares) | | | 20,500 | |
Deferred Restricted Stock plan activity, Weighted Average Fair Value at Grant Date | | | | |
Outstanding at beginning of period (in dollars per share) | | | $ 22.64 | |
Granted (in dollars per share) | | | 44.07 | |
Vested and deferred (in dollars per share) | | | 22.64 | |
Outstanding at end of period (in dollars per share) | $ 44.07 | | 44.07 | |
Vested and deferred (in dollars per share) | | | $ 29.23 | |
Restricted stock plan activity, other disclosures | | | | |
Compensation expense | $ 42 | 42 | | |
Remaining unrecognized compensation expense | $ 112 | | $ 112 | |
Weighted average period for recognition | | | 8 months 1 day | |
Repurchase of stock from employees (in shares) | | | 1,151 | |
Average purchase price (in dollars per share) | $ 41.78 | | $ 41.78 | |
Performance Shares | Certain Employees | | | | |
Stock-Based Compensation | | | | |
Remaining unrecognized compensation expense | $ 1,811 | | $ 1,811 | |
Restricted stock plan activity, number of shares | | | | |
Unvested and deferred at beginning of the period (in shares) | | | 87,193 | |
Granted (in shares) | | | 21,520 | |
Forfeited / Canceled (in shares) | | | (8,172) | |
Vested and deferred (in shares) | | | (24,121) | |
Unvested and deferred at end of the period (in shares) | 76,420 | | 76,420 | |
Restricted stock plan activity, Weighted Average Fair Value at Grant Date | | | | |
Unvested and deferred at beginning of the period (in dollars per share) | | | $ 37.24 | |
Granted (in dollars per share) | | | 61.04 | |
Forfeited / Canceled (in dollars per share) | | | 42.97 | |
Vested and deferred (in dollars per share) | | | 43.42 | |
Unvested and deferred at end of the period (in dollars per share) | $ 41.37 | | $ 41.37 | |
Deferred Restricted Stock plan activity, number of shares | | | | |
Vested (in shares) | | | 24,121 | |
Deferred Restricted Stock plan activity, Weighted Average Fair Value at Grant Date | | | | |
Vested and deferred (in dollars per share) | | | $ 43.42 | |
Restricted stock plan activity, other disclosures | | | | |
Compensation expense | $ 224 | $ 287 | $ 453 | $ 509 |
Weighted average period for recognition | | | 1 year 7 months 2 days | |