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Stock-based Compensation Plans (Schedule of Shared-Based Compensation, Performance Units (Details)	3 Months Ended						12 Months Ended
	Dec. 31, 2017 shares	Mar. 31, 2017 shares	Dec. 31, 2016 shares	Dec. 31, 2015 shares	Dec. 31, 2014 shares	Dec. 31, 2013 shares	Sep. 30, 2021 shares	Sep. 30, 2020 shares	Sep. 30, 2019 shares	Sep. 30, 2018 $ / shares shares	Sep. 30, 2017 $ / shares shares	Sep. 30, 2016 $ / shares shares	Sep. 30, 2015 $ / shares shares	Sep. 30, 2014 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period											160,063
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										86,516		335,998
Settlement of performance-based restricted stock units, net of shares withheld for taxes										146,061	263,410
Share-based Compensation Award, 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
2014 [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 | $ / shares												$ 9.38	$ 9.78	$ 8.52
2014 [Member] | Share-based Compensation Award, Tranche One [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor														2.000
Settlement of performance-based restricted stock units, net of shares withheld for taxes											172,880
2014 [Member] | Share-based Compensation Award, 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														90,841
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period														(4,401)
Settlement of performance-based restricted stock units, net of shares withheld for taxes											86,440
2014 [Member] | Share-based Compensation Award, Tranche Two [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor													0.000
Settlement of performance-based restricted stock units, net of shares withheld for taxes											0
2014 [Member] | Share-based Compensation Award, 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						90,841
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period													(4,401)
Settlement of performance-based restricted stock units, net of shares withheld for taxes											86,440
2014 [Member] | Share-based Compensation Award, Tranche Three [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor												1.021
Settlement of performance-based restricted stock units, net of shares withheld for taxes											85,199
2014 [Member] | Share-based Compensation Award, 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						90,849
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period												(7,402)
Settlement of performance-based restricted stock units, net of shares withheld for taxes											83,447
2015 [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 | $ / shares											$ 13.26
2015 [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 | $ / shares												$ 9.38	$ 9.78
2015 [Member] | Share-based Compensation Award, Tranche One [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor													0.000
Settlement of performance-based restricted stock units, net of shares withheld for taxes										0
2015 [Member] | Share-based Compensation Award, 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					80,233
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period													(3,835)
Settlement of performance-based restricted stock units, net of shares withheld for taxes										76,398
2015 [Member] | Share-based Compensation Award, Tranche Two [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor												1.021
Settlement of performance-based restricted stock units, net of shares withheld for taxes										75,327
2015 [Member] | Share-based Compensation Award, 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					80,229
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period												(6,447)
Settlement of performance-based restricted stock units, net of shares withheld for taxes										73,782
2015 [Member] | Share-based Compensation Award, Tranche Three [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor											1.000
Settlement of performance-based restricted stock units, net of shares withheld for taxes										68,556
2015 [Member] | Share-based Compensation Award, 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					80,229
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period											(11,673)
Settlement of performance-based restricted stock units, net of shares withheld for taxes										68,556
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 | $ / shares										$ 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 | $ / shares												$ 9.38
2016 [Member] | Share-based Compensation Award, Tranche One [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor												1.021
2016 [Member] | Share-based Compensation Award, 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 Compensation Award, Tranche Two [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor											1.000
2016 [Member] | Share-based Compensation Award, 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 Compensation Award, Tranche Three [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor										1.357
2016 [Member] | Share-based Compensation Award, 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 | $ / shares										$ 12.50	$ 13.26
2017 member [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor											1.000
2017 member [Member] | Share-based Compensation Award, 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 Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor										1.357
2017 member [Member] | Share-based Compensation Award, 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 Compensation Award, 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
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 | $ / shares											$ 13.15
January 23, 2017 [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor											1.000
January 23, 2017 [Member] | Share-based Compensation Award, 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 Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor										1.357
January 23, 2017 [Member] | Share-based Compensation Award, 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
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number										19,011
January 23, 2017 [Member] | Share-based Compensation Award, 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 | $ / shares										$ 12.50
November 28, 2017 [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Factor										1.357
November 28, 2017 [Member] | Share-based Compensation Award, 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
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period										0
November 28, 2017 [Member] | Share-based Compensation Award, 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
November 28, 2017 [Member] | Share-based Compensation Award, 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
Scenario, Forecast [Member] | 2016 [Member] | Share-based Compensation Award, Tranche One [Member] | Performance Shares [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									75,375
Scenario, Forecast [Member] | 2016 [Member] | Share-based Compensation Award, Tranche Two [Member] | Performance Shares [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									73,827
Scenario, Forecast [Member] | 2016 [Member] | Share-based Compensation Award, Tranche Three [Member] | Performance Shares [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									21,689
Scenario, Forecast [Member] | 2017 member [Member] | Share-based Compensation Award, 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								54,006
Scenario, Forecast [Member] | 2017 member [Member] | Share-based Compensation Award, 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								26,294
Scenario, Forecast [Member] | 2017 member [Member] | Share-based Compensation Award, 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									(39,909)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number									19,381
Scenario, Forecast [Member] | January 23, 2017 [Member] | Share-based Compensation Award, 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								19,012
Scenario, Forecast [Member] | January 23, 2017 [Member] | Share-based Compensation Award, 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								25,798
Scenario, Forecast [Member] | January 23, 2017 [Member] | Share-based Compensation Award, 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, Nonvested, Number									19,011
Scenario, Forecast [Member] | January 23, 2017 [Member] | Share-based Compensation Award, 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									0
Scenario, Forecast [Member] | 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, Grants in Period								57,104	57,092
Scenario, Forecast [Member] | November 28, 2017 [Member] | Share-based Compensation Award, 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
Scenario, Forecast [Member] | November 27, 2018 [Member] | Share-based Compensation Award, 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									0
Scenario, Forecast [Member] | November 27, 2018 [Member] | Share-based Compensation Award, 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								0

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