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Long-Term Incentive Plan - Additional Information (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Compensation Related Costs [Abstract]        
Contributions to plan by employer   $ 0.3   $ 0.6
Deferred compensation expense $ 0.2 0.3 $ 0.7  
Deferred compensation liability   $ 2.0   $ 3.1