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Equity-Based Compensation Plans Summary of Status of Outstanding Performance Share Awards (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
Mar. 31, 2017
Dec. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Percentage of performance share payout measured by total shareholder return 40.00%     40.00%      
Percentage of performance share payout measured by return on invested capital 60.00%     60.00%      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term       7 years 5 months      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number 131,947 137,860   131,947      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]              
Beginning Balance   527,054   527,054 277,693 150,580  
Granted       158,484 280,191 142,542  
Forfeited       (22,306) (30,830) (15,429)  
Ending Balance 657,319   527,054 657,319 527,054 277,693  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]              
Granted       $ 56.45 $ 38.86 $ 61.93  
Aggregate intrinsic value              
Aggregate intrinsic value $ 0   $ 7 $ 0 $ 7 $ 0 $ 0
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage     89.00%        
Performance shares              
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, Vested Shares Settled 41,538     0      
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Settled and Distributed In Period     45,953        
Number of share              
Ending Balance 117,252   175,683 117,252 175,683 92,563  
Granted       33,907 93,397 47,513  
Settled       (87,491) 0 (245,525)  
Forfeited       (4,847) (10,277) (10,289)  
Beginning Balance   175,683   175,683 92,563 300,864  
Weighted Average Grant Date Fair Value              
Beginning Balance   $ 62.26   $ 62.26 $ 84.18 $ 59.77  
Granted       58.58 39.70 62.05  
Settled       84.65 0.00 50.43  
Forfeited       47.61 54.55 73.61  
Ending Balance $ 45.10   $ 62.26 $ 45.10 $ 62.26 $ 84.18  
Aggregate intrinsic value              
Aggregate intrinsic value $ 5,323   $ 11,516 $ 5,323 $ 11,516 $ 4,214  
Shares Issued Net Of Shares For Tax Withholdings   27,878          
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized $ 2,300     $ 2,300      
Maximum [Member] | Employee Stock Option [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period       10 years      
Maximum [Member] | Performance shares              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share Based Compensation Arrangement By Share Based Payment Award Outstanding Award As Percentage Of Shares Issued     200.00%   200.00%    
Minimum [Member] | Performance shares              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share Based Compensation Arrangement By Share Based Payment Award Outstanding Award As Percentage Of Shares Issued     0.00%   0.00%