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Stock-Based Compensation - Narrative (Details)
$ / shares in Units, $ in Thousands
1 Months Ended 3 Months Ended 12 Months Ended
Jun. 01, 2014
shares
Jul. 31, 2017
$ / shares
shares
Feb. 28, 2017
installment
$ / shares
shares
Dec. 31, 2017
USD ($)
shares
Dec. 31, 2017
USD ($)
shares
Dec. 31, 2016
USD ($)
shares
Dec. 31, 2015
USD ($)
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Compensation expense associated with grants | $         $ 2,416 $ 1,546 $ 1,522
Number of restricted stock awards granted (shares)         254,534    
Restricted Stock Awards              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Compensation expense associated with grants | $         $ 2,400 $ 1,500 $ 1,500
Unamortized stock-based compensation expense related to unvested awards | $       $ 3,800 $ 3,800    
Weighted average remaining vesting period related to expense recognition         1 year 9 months 18 days    
Shares vested (shares)         111,024 121,899  
Unvested stock awards outstanding (shares)       422,911 422,911 286,068 394,697
Number of restricted stock awards granted (shares)           20,770  
Restricted Stock Awards | Ensign Employees              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Restricted stock award conversion ratio related to the spin-off 1            
Stock awards unvested during spin-off (shares) 207,580            
Shares vested (shares)       27,200      
Unvested stock awards outstanding (shares)       14,980 14,980    
Restricted Stock Awards | Board of Directors              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Number of restricted stock awards granted (shares)   20,766 233,768        
Restricted stock awards grant date fair value (usd per share) | $ / shares   $ 18.30 $ 15.21        
Number of equal annual vesting installments | installment     3