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Stock-based Compensation Plans (Narrative) (Details) $ / shares in Units, $ in Millions | 3 Months Ended | 6 Months Ended | 9 Months Ended
--- | --- | --- | ---
Jun. 30, 2019 USD ($) $ / shares shares | Jun. 30, 2018 USD ($) shares | Mar. 31, 2019 | Jun. 30, 2019 USD ($) $ / shares shares | Jun. 30, 2018 USD ($) shares
Share-based Payment Arrangement, Expense | $ | $ 1.4 | $ 1.2 |  | $ 4.2 | $ 5.3
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount | $ |  | $ 7.7 |  |  | $ 7.7
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | 202,245 | 213,599 |  | 167,775 | 245,033
Phantom Share Units (PSUs) [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instrument Other than Option, Nonvested, Intrinsic Value | $ / shares | $ 9.82 |  |  | $ 9.82 |
Share-based compensation liability | $ | $ 1.3 |  |  | $ 1.3 |
Performance Shares [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period |  |  |  | 181,065 | 146,061
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  | 332,875 |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period |  |  | 3 years |  |
Share-based compensation, units awarded but not yet granted |  | 264,936 |  |  | 264,936
Restricted Stock Units (RSUs) [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period | 0 |  |  | 259,107 |
Minimum [Member] | Performance Shares [Member] |  |  |  |  |
Performance Factor |  |  | 0 |  |
Maximum [Member] | Performance Shares [Member] |  |  |  |  |
Performance Factor |  |  | 2 |  |

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