XML 121 R74.htm IDEA: XBRL DOCUMENT v3.10.0.1
Stock-based Compensation - (Details) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 12 Months Ended
Aug. 07, 2014
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Non-cash share compensation         $ 8,681 $ 6,695 $ 5,672  
2013 Plan | Restricted common shares                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Number of shares authorized 2,450,000             600,000
Number of additional shares authorized 1,850,000              
Granted (in shares)         206,446 143,593 155,306  
Share-based compensation, gross           $ 2,800 $ 2,800  
Non-cash share compensation         $ 3,100 3,100 3,600  
Unrecognized compensation expense         $ 1,000 $ 1,000 $ 1,200  
Grant date value (in dollars per share)         $ 14.87 $ 19.74 $ 17.96  
2013 Plan | Restricted common shares | Minimum                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Vesting period         1 year 1 year 1 year  
2013 Plan | Restricted common shares | Maximum                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Vesting period         3 years 3 years 3 years  
2013 Plan | Restricted Share Units                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Non-cash share compensation         $ 5,500 $ 3,600 $ 2,100  
Unrecognized compensation expense         $ 5,200 $ 5,000 $ 2,800  
2013 Plan | Trustee Awards, Restricted Stock Units (RSUs)                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Granted (in shares)         50,745 32,831 36,784  
Grant date value (in dollars per share)         $ 14.78 $ 19.80 $ 17.67  
2013 Plan | Market Based RSU                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Grant date value (in dollars per share)         $ 19.28 $ 33.43 $ 28.50  
2013 Plan | Performance based restricted stock units                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Grant date value (in dollars per share)   $ 16.58 $ 29.34 $ 26.33        
Grant date fair value (in dollars per share)   $ 14.78 $ 19.80 $ 17.67        
Officers and Certain Employees | 2013 Plan | Restricted common shares                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Granted (in shares)         206,446      
Share-based compensation, gross         $ 3,100      
Officer | 2013 Plan | Restricted Share Units                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Granted (in shares)   254,282 174,320 104,553        
Vesting period         3 years      
Officer | 2013 Plan | Market Based RSU                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Percentage of shares awarded         40.00% 70.00% 80.00%  
Officer | 2013 Plan | Performance based restricted stock units                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Percentage of shares awarded         60.00% 30.00% 20.00%  
Trustees | 2013 Plan | Restricted Share Units                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Vesting period         2 years      
Trustees | 2013 Plan | Trustee Awards, Restricted Stock Units (RSUs)                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Granted (in shares)   50,745 32,831 36,784        
Trustees | 2013 Plan | Restricted Share Units                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Number of dividend equivalent included in award         1