XML 100 R84.htm IDEA: XBRL DOCUMENT
v3.20.2

Stock-based Compensation Plans (Schedule of Shared-Based Compensation, Performance Units (Details) - $ / shares |  |  |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Feb. 24, 2020 | Jan. 28, 2020 | Dec. 03, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | 7,498 | 2,763 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividend yield | 1.73% | 1.76% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk-free interest rate | 1.23% | 1.44% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expected life (years) | 2 years 7 months 6 days | 2 years 8 months 1 day |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period |  |  |  |  |  |  |  |  |  |  |  |  |  | 109,380 |  |  |
Granted, Weighted average grant date fair value per share | $ 18.17 | $ 16.76 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity |  |  |  |  |  |  |  |  |  |  |  |  | Restricted stock unit activity under the 2006 Plan is summarized below.
| Restricted stock units |  | Weighted average grant date fair value per unit |  | Weighted average remaining contractual term (years) |  | Aggregate intrinsic value (millions)
Outstanding at September 30, 2017 | 625,830 |  |  | $ | 11.23 |  |  | 0.9 |  |
Granted | 276,658 |  |  | 12.20 |  |  |  |  |
Vested | (342,038) |  |  | 10.84 |  |  |  |  | $ | 4.2 |
Cancelled | (78,888) |  |  | 11.41 |  |  |  |  |
Outstanding at September 30, 2018 | 481,562 |  |  | 12.14 |  |  | 1.0 |  |
Granted | 233,830 |  |  | 10.10 |  |  |  |  |
Vested | (259,107) |  |  | 11.75 |  |  |  |  | 2.6 |
Cancelled | (19,263) |  |  | 11.43 |  |  |  |  |
Outstanding at September 30, 2019 | 437,022 |  |  | 11.31 |  |  | 0.9 |  |
Granted | 301,979 |  |  | 11.55 |  |  |  |  |
Vested | (295,241) |  |  | 11.40 |  |  |  |  | 3.4 |
Cancelled | (35,254) |  |  | 11.48 |  |  |  |  |
Outstanding at September 30, 2020 | 408,506 |  |  | 11.41 |  |  | 0.8 |  |
Performance Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period |  |  |  |  |  |  |  |  |  |  |  |  | 61,610 |  | 86,516 |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  | 93,647,000,000 | 181,065 |  |  |
Market Based Performance Shares Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  | 147,213 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividend yield |  |  | 1.87% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk-free interest rate |  |  | 1.53% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expected life (years) |  |  | 2 years 9 months 29 days |  |  |  |  |  |  |  |  |  |  |  |  |  |
Granted, Weighted average grant date fair value per share |  |  | $ 14.94 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Payment Arrangement, Tranche One [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  | 57,092 |  |  |  |  |  |  |  |  |  |  |
2016 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 12.50 | $ 13.26 |
2016 [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 9.38
2016 [Member] | Share-based Payment Arrangement, Tranche One [Member] | Performance Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 102.10%
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  |  | 75,375 |  |  |
2016 [Member] | Share-based Payment Arrangement, Tranche One [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  |  |  |  | 77,823 |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (3,998)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 73,825
2016 [Member] | Share-based Payment Arrangement, Tranche Two [Member] | Performance Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  |  | 73,827 |  |  |
2016 [Member] | Share-based Payment Arrangement, Tranche Two [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  |  |  |  | 77,824 |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (3,997) |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 73,827 |
2016 [Member] | Share-based Payment Arrangement, Tranche Three [Member] | Performance Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 135.70% |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  |  | 21,689 |  |  |
2016 [Member] | Share-based Payment Arrangement, Tranche Three [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  |  |  |  | 77,824 |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (61,841) |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15,983 |  |
2017 member [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 10.53 | $ 12.50 | $ 13.26 |
2017 member [Member] | Share-based Payment Arrangement, Tranche One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  | 54,006 |  |  |  |
2017 member [Member] | Share-based Payment Arrangement, Tranche One [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  |  |  | 59,285 |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (5,279) |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 54,006 |
2017 member [Member] | Share-based Payment Arrangement, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 135.70% |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  | 26,294 |  |  |  |
2017 member [Member] | Share-based Payment Arrangement, Tranche Two [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  |  |  | 59,286 |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (39,910) |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 19,376 |  |
2017 member [Member] | Share-based Payment Arrangement, Tranche Three [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  | 64.50% |  |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  | 12,501 |  |  |  |
2017 member [Member] | Share-based Payment Arrangement, Tranche Three [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  |  |  | 59,290 |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  | (39,909) |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  | 19,381 |  |  |
January 23, 2017 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 13.15 |
January 23, 2017 [Member] | Share-based Payment Arrangement, Tranche One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  | 19,012 |  |  |  |
January 23, 2017 [Member] | Share-based Payment Arrangement, Tranche One [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  |  | 19,012 |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 19,012 |
January 23, 2017 [Member] | Share-based Payment Arrangement, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 135.70% |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  | 25,798 |  |  |  |
January 23, 2017 [Member] | Share-based Payment Arrangement, Tranche Two [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  |  | 19,011 |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  | 19,011 | 19,011 |  |
January 23, 2017 [Member] | Share-based Payment Arrangement, Tranche Three [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  | 64.50% |  |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  |  | 12,263 |  |  |  |
January 23, 2017 [Member] | Share-based Payment Arrangement, Tranche Three [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  |  | 19,011 |  |  |  |  |  |  |  |  |  |
November 28, 2017 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |  |  |  | $ 11.26 | $ 10.53 | $ 12.50 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  | 35,425 | 52,299 |  |  |
November 28, 2017 [Member] | Share-based Payment Arrangement, Tranche One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 135.70% |  |
November 28, 2017 [Member] | Share-based Payment Arrangement, Tranche One [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 57,092 |  |
November 28, 2017 [Member] | Share-based Payment Arrangement, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  | 64.50% |  |  |
November 28, 2017 [Member] | Share-based Payment Arrangement, Tranche Two [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  | 57,092 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  | (4,793) |  |  |
November 28, 2017 [Member] | Share-based Payment Arrangement, Tranche Three [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  | 90.90% |  |  |  |
November 28, 2017 [Member] | Share-based Payment Arrangement, Tranche Three [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  |  | 57,104 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  | (21,679) |  |  |  |
November 27, 2018 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |  |  |  | $ 11.26 | $ 10.53 |  |  |
November 27, 2018 [Member] | Share-based Payment Arrangement, Tranche One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  |  | 102,203 |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  |  | 64.50% |  |  |
November 27, 2018 [Member] | Share-based Payment Arrangement, Tranche One [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  | 110,954 |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  |  | (8,751) |  |  |
November 27, 2018 [Member] | Share-based Payment Arrangement, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  | 97,772 |  |  |  |
November 27, 2018 [Member] | Share-based Payment Arrangement, Tranche Two [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  | 110,954 |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  | (13,182) |  |  |  |
November 27, 2018 [Member] | Share-based Payment Arrangement, Tranche Three [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  | 84,483 |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  | 90.90% |  |  |  |
November 27, 2018 [Member] | Share-based Payment Arrangement, Tranche Three [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  | 110,967 |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  | (26,484) |  |  |  |
December 3, 2019 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |  |  |  | $ 11.26 |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  | 60,019 |  |  |  |
December 3, 2019 | Share-based Payment Arrangement, Tranche One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  | 67,241 |  |  |  |
December 3, 2019 | Share-based Payment Arrangement, Tranche One [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  | 69,988 |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  |  | (2,747) |  |  |  |
December 3, 2019 | Share-based Payment Arrangement, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number |  |  |  |  |  |  |  |  |  |  |  |  | 60,019 |  |  |  |
December 3, 2019 | Share-based Payment Arrangement, Tranche Two [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  | 69,989 |  |  |  |  |  |  |  |  |  |  |  |  |
December 3, 2019 | Share-based Payment Arrangement, Tranche Three [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Factor |  |  |  |  |  |  |  |  |  |  |  |  | 90.90% |  |  |  |
December 3, 2019 | Share-based Payment Arrangement, Tranche Three [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  | 69,989 |  |  |  |  |  |  |  |  |  |  |  |  |
Forecast [Member] | November 28, 2017 [Member] | Share-based Payment Arrangement, Tranche One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  | 77,474 |  |  |  |  |
Forecast [Member] | November 28, 2017 [Member] | Share-based Payment Arrangement, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  | 33,733 |  |  |  |  |
Forecast [Member] | November 28, 2017 [Member] | Share-based Payment Arrangement, Tranche Three [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  |  | 32,202 |  |  |  |  |
Forecast [Member] | November 27, 2018 [Member] | Share-based Payment Arrangement, Tranche One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  | 65,921 |  |  |  |  |  |
Forecast [Member] | November 27, 2018 [Member] | Share-based Payment Arrangement, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  |  | 88,875 |  |  |  |  |  |
Forecast [Member] | December 3, 2019 | Share-based Payment Arrangement, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement of performance-based restricted stock units, net of shares withheld for taxes |  |  |  |  |  |  |  |  |  | 61,123 |  |  |  |  |  |  |
Forecast [Member] | December 3, 2019 | Share-based Payment Arrangement, Tranche Two [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  |  | (9,970) |  |  |  |  |
Forecast [Member] | December 3, 2019 | Share-based Payment Arrangement, Tranche Three [Member] | PRSU base units [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period |  |  |  |  |  |  |  |  |  |  | (9,970) |  |  |  |  |  |

X
- Definition Coefficient multiplied by the number of Performance Units to determine the number of shares of common stock, or the dollar-value equivalent thereof, upon settlement. + References No definition available. + Details
Name: | mwa_PerformanceFactor
Namespace Prefix: | mwa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of the number and weighted-average grant date fair value for restricted stock and restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock and restricted stock units that were granted, vested, or forfeited during the year. + References No definition available. + Details
Name: | us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iv) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares issued under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.D.2) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 + Details
Name: | us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=mwa_MarketBasedPerformanceSharesMemberMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=mwa_PRSUbaseunitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardDateAxis=mwa_A2016Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardDateAxis=mwa_A2017memberMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardDateAxis=mwa_January232017Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardDateAxis=mwa_November282017Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardDateAxis=mwa_November272018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardDateAxis=mwa_December32019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |