Share Repurchases (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Feb. 28, 2018
Equity, Class of Treasury Stock [Line Items]      
Common stock authorized for repurchase $ 12,600    
Number of common stock repurchased (in shares) 300,000 119,007  
Value of common stock repurchased $ 7,448 $ 1,821  
Maximum      
Equity, Class of Treasury Stock [Line Items]      
Common stock authorized for repurchase     $ 20,000