Long-term Equity-based Compensation Plans Schedule of Nonvested Restricted Stock Units Activity (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 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
Restricted Stock, Nonvested at Beginning of Year, Weighted Average Grant Date Fair Value	$ 32.42
Restricted Stock, Grants in Period	0
Restricted Stock, Weighted Average Grant Date Fair Value	$ 0.00
Restricted Stock, Vested in Period	(500)
Restricted Stock, Vested in Period, Weighted Average Grant Date Fair Value	$ 29.02
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	47,781
Restricted Stock, Nonvested at End of Period, Weighted Average Grant Date Fair Value	$ 32.73
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
Restricted Stock, Nonvested at Beginning of Year, Weighted Average Grant Date Fair Value	$ 36.60
Restricted Stock, Grants in Period	67,375
Restricted Stock, Weighted Average Grant Date Fair Value	$ 36.65
Restricted Stock, Vested in Period	0
Restricted Stock, Vested in Period, Weighted Average Grant Date Fair Value	$ 0.00
Restricted Stock, Forfeited in Period	(1,775)
Restricted Stock, Forfeitures, Weighted Average Grant Date Fair Value	$ 36.13
Restricted Stock, Nonvested at End of Period, Number	95,624
Restricted Stock, Nonvested at End of Period, Weighted Average Grant Date Fair Value	$ 36.64
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
Restricted Stock, Nonvested at Beginning of Year, Weighted Average Grant Date Fair Value	$ 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
Restricted Stock, Nonvested at Beginning of Year, Weighted Average Grant Date Fair Value	$ 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	(1,800)
Restricted Stock, Forfeitures, Weighted Average Grant Date Fair Value	$ 41.49
Restricted Stock, Nonvested at End of Period, Number	128,900
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		$ 2.4
Restricted Stock, Vested in Period, Tax Benefits		$ 0.8
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	68,125
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	60,775
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