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Stock Based Compensation Plan (Details) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Additional Disclosures [Abstract]    
Stock based compensation expense $ 1.6 $ 1.3
Total compensation cost related to unvested equity awards $ 7.8  
Weighted-average period of recognition of cost 2 years 6 months  
Service-Based Restricted Stock Awards [Member]    
Shares or Units and Rights [Roll Forward]    
Outstanding, beginning balance (in shares) 254,490  
Granted/Issued (in shares) 116,035  
Awards vested or rights exercised (in shares) [1] 0  
Forfeited (in shares) (400)  
Outstanding, ending balance (in shares) 370,125  
Exercisable, ending balance (in shares) 0  
Awards expected to vest (in shares) 370,125  
Weighted-Average Award Price [Roll Forward]    
Outstanding, beginning balance (in dollars per share) $ 21.88  
Granted/Issued (in dollars per share) 22.95  
Awards vested or rights exercised (in dollars per share) [1] 0  
Forfeited (in dollars per share) 22.38  
Outstanding, ending balance (in dollars per share) 22.21  
Exercisable, ending balance (in dollars per share) 0  
Awards expected to vest (in dollars per share) $ 22.21  
Additional Disclosures [Abstract]    
Aggregate intrinsic value of outstanding awards $ 7.5  
Service-Based Restricted Stock Awards [Member] | Minimum [Member]    
Additional Disclosures [Abstract]    
Vesting period of awards 1 year  
Service-Based Restricted Stock Awards [Member] | Maximum [Member]    
Additional Disclosures [Abstract]    
Vesting period of awards 4 years  
Performance-Based Restricted Stock Awards [Member]    
Shares or Units and Rights [Roll Forward]    
Outstanding, beginning balance (in shares) 179,774  
Granted/Issued (in shares) 103,940  
Awards vested or rights exercised (in shares) [1] (46,269)  
Forfeited (in shares) (7,033)  
Outstanding, ending balance (in shares) 230,412  
Exercisable, ending balance (in shares) 0  
Awards expected to vest (in shares) 214,481  
Weighted-Average Award Price [Roll Forward]    
Outstanding, beginning balance (in dollars per share) $ 21.42  
Granted/Issued (in dollars per share) 22.95  
Awards vested or rights exercised (in dollars per share) [1] 20.35  
Forfeited (in dollars per share) 0  
Outstanding, ending balance (in dollars per share) 21.60  
Exercisable, ending balance (in dollars per share) 0  
Awards expected to vest (in dollars per share) $ 21.58  
Additional Disclosures [Abstract]    
Vesting period of awards 3 years  
Fair value of vested shares $ 1.1  
Aggregate intrinsic value of outstanding awards $ 4.6  
Stock-Settled Appreciation Rights [Member]    
Shares or Units and Rights [Roll Forward]    
Outstanding, beginning balance (in shares) 57,000  
Granted/Issued (in shares) 0  
Awards vested or rights exercised (in shares) [1] 0  
Forfeited (in shares) 0  
Outstanding, ending balance (in shares) 57,000  
Exercisable, ending balance (in shares) 57,000  
Awards expected to vest (in shares) 0  
Weighted-Average Award Price [Roll Forward]    
Outstanding, beginning balance (in dollars per share) $ 18.14  
Granted/Issued (in dollars per share) 0  
Awards vested or rights exercised (in dollars per share) [1] 0  
Forfeited (in dollars per share) 0  
Outstanding, ending balance (in dollars per share) 18.14  
Exercisable, ending balance (in dollars per share) 18.14  
Awards expected to vest (in dollars per share) $ 0  
Additional Disclosures [Abstract]    
Aggregate intrinsic value of outstanding awards $ 0.1  
Aggregate intrinsic value of vested awards $ 0.1  
[1] Includes shares repurchased from employees for employee's tax liability.