Long-term Equity-based Compensation Plans Schedule of Nonvested Restricted Stock Units Activity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2015	Sep. 30, 2015	Sep. 30, 2014
Time Vested Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock, Nonvested at Beginning of Year, Number	53,095	53,095
Restricted Stock, Nonvested at Beginning of Year, Weighted Average Grant Date Fair Value	$ 32.42	$ 32.42
Restricted Stock, Grants in Period		0
Restricted Stock, Weighted Average Grant Date Fair Value		$ 0.00
Restricted Stock, Vested in Period		(18,733)
Restricted Stock, Vested in Period, Weighted Average Grant Date Fair Value		$ 31.09
Restricted Stock, Forfeited in Period		(4,814)
Restricted Stock, Forfeitures, Weighted Average Grant Date Fair Value		$ 29.39
Restricted Stock, Nonvested at End of Period, Number		29,548
Restricted Stock, Nonvested at End of Period, Weighted Average Grant Date Fair Value		$ 33.76
Time Vested Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock, Nonvested at Beginning of Year, Number	30,024	30,024
Restricted Stock, Nonvested at Beginning of Year, Weighted Average Grant Date Fair Value	$ 36.60	$ 36.60
Restricted Stock, Grants in Period		67,375
Restricted Stock, Weighted Average Grant Date Fair Value		$ 36.65
Restricted Stock, Vested in Period		(16,701)
Restricted Stock, Vested in Period, Weighted Average Grant Date Fair Value		$ 36.33
Restricted Stock, Forfeited in Period		(2,075)
Restricted Stock, Forfeitures, Weighted Average Grant Date Fair Value		$ 36.16
Restricted Stock, Nonvested at End of Period, Number		78,623
Restricted Stock, Nonvested at End of Period, Weighted Average Grant Date Fair Value		$ 36.71
Performance Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock, Nonvested at Beginning of Year, Number	110,625	110,625
Restricted Stock, Nonvested at Beginning of Year, Weighted Average Grant Date Fair Value	$ 39.28	$ 39.28
Restricted Stock, Grants in Period		0
Restricted Stock, Weighted Average Grant Date Fair Value		$ 0.00
Restricted Stock, Vested in Period		0
Restricted Stock, Vested in Period, Weighted Average Grant Date Fair Value		$ 0.00
Restricted Stock, Forfeited in Period		(59,225)
Restricted Stock, Forfeitures, Weighted Average Grant Date Fair Value		$ 36.81
Restricted Stock, Nonvested at End of Period, Number		51,400
Restricted Stock, Nonvested at End of Period, Weighted Average Grant Date Fair Value		$ 42.12
Performance Period		3 years
Performance Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock, Nonvested at Beginning of Year, Number	61,875	61,875
Restricted Stock, Nonvested at Beginning of Year, Weighted Average Grant Date Fair Value	$ 40.50	$ 40.50
Restricted Stock, Grants in Period		68,825
Restricted Stock, Weighted Average Grant Date Fair Value		$ 43.05
Restricted Stock, Vested in Period		0
Restricted Stock, Vested in Period, Weighted Average Grant Date Fair Value		$ 0.00
Restricted Stock, Forfeited in Period		(2,600)
Restricted Stock, Forfeitures, Weighted Average Grant Date Fair Value		$ 41.68
Restricted Stock, Nonvested at End of Period, Number		128,100
Restricted Stock, Nonvested at End of Period, Weighted Average Grant Date Fair Value		$ 41.85
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock, Vested in Period, Total Fair Value	$ 1.4		$ 3.6
Restricted Stock, Vested in Period, Tax Benefits	$ 0.5		$ 1.2
Performance Period, 2015 to 2017 [Member] | Performance Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Additional Shares To Be Granted If Maximum Perfornance Level Is Met or Exceeded		67,625
Performance Period, 2014 to 2016 [Member] | Performance Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Additional Shares To Be Granted If Maximum Perfornance Level Is Met or Exceeded		60,475
Performance Period, 2013 to 2015 [Member] | Performance Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Additional Shares To Be Granted If Maximum Perfornance Level Is Met or Exceeded		51,400
Performance Period, 2012 to 2014 [Member] | Performance Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, Share-based Compensation, Forfeited		57,775