v3.8.0.1
Credit Facility (Details) - USD ($)
$ in Thousands
1 Months Ended 12 Months Ended
Feb. 29, 2016
Aug. 31, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Jan. 31, 2016
Credit Facility            
Additional debt issuance costs incurred     $ 0 $ 124 $ 62  
Credit Facility            
Credit Facility            
Interest rate percentage     3.80%      
Additional debt issuance costs incurred $ 124 $ 62        
Amortization and interest expense capitalized     $ 773 823 $ 648  
Amortization and interest expense expensed     $ 187 309    
Credit Facility | Minimum            
Credit Facility            
Interest rate percentage     3.50%      
Credit Facility | Maximum            
Credit Facility            
Interest rate percentage     3.80%      
Credit Facility | LIBOR | Minimum            
Credit Facility            
Spread on floating interest rate (as a percent)     2.50%      
Credit Facility | LIBOR | Maximum            
Credit Facility            
Spread on floating interest rate (as a percent)     3.50%      
Credit Facility | Prime Rate | Minimum            
Credit Facility            
Spread on floating interest rate (as a percent)     1.50%      
Credit Facility | Prime Rate | Maximum            
Credit Facility            
Spread on floating interest rate (as a percent)     2.50%      
Revolving Line of Credit            
Credit Facility            
Current issued borrowing capacity $ 69,750     69,750   $ 46,500
Maximum borrowing capacity with an option to increase the available amount upon the satisfaction of certain conditions     $ 86,500      
Outstanding balance     $ 0 15,000    
Revolving Line of Credit | Minimum            
Credit Facility            
Fee on unused portion of Revolving Line of Credit(as a percent)     0.375%      
Revolving Line of Credit | Maximum            
Credit Facility            
Fee on unused portion of Revolving Line of Credit(as a percent)     0.50%      
Term Loan            
Credit Facility            
Current issued borrowing capacity     $ 3,500      
Outstanding balance     $ 875 $ 1,969    
Term of the debt     4 years