Quarterly report pursuant to Section 13 or 15(d)

Treasury Stock - Additional Information (Details)

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Treasury Stock - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions
1 Months Ended 3 Months Ended 5 Months Ended 9 Months Ended 14 Months Ended
Aug. 07, 2018
Aug. 31, 2017
Sep. 30, 2018
Dec. 31, 2017
Sep. 30, 2018
Sep. 30, 2018
Share Repurchase Program August 2017            
Equity Class Of Treasury Stock [Line Items]            
Common stock repurchase, value     $ 3.1   $ 3.1 $ 3.1
Common Stock            
Equity Class Of Treasury Stock [Line Items]            
Stock repurchase, shares       135,000    
Common Stock | Share Repurchase Program August 2017            
Equity Class Of Treasury Stock [Line Items]            
Stock approved for repurchase, value   $ 7.0        
Period of stock repurchase program   12 months        
Additional period of stock repurchase program 12 months          
Stock repurchase, shares     42,995   193,523 328,523
Stock repurchase, average price per share     $ 11.95   $ 9.49  
Stock repurchase, cost     $ 0.5   $ 1.8