Quarterly report pursuant to Section 13 or 15(d)

Repurchase of Common Stock (Details)

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Repurchase of Common Stock (Details) - USD ($)
 1 Months Ended 3 Months Ended 9 Months Ended
Jun. 30, 2018
Jun. 02, 2018
May 05, 2018
Jun. 30, 2018
Jun. 30, 2018
Class of Stock [Line Items]          
Authorized amount $ 50,000,000     $ 50,000,000 $ 50,000,000
Shares repurchased (in shares)       63,300  
Aggregated number of shares repurchased (in shares) 3,173,845     3,173,845 3,173,845
Aggregated shares repurchased, value $ 44,400,000     $ 44,400,000 $ 44,400,000
Dollar value of shares that may yet be purchased under the plans $ 5,600,000     $ 5,600,000 5,600,000
Stock repurchased during period, value         1,200,000
Common Stock          
Class of Stock [Line Items]          
Shares repurchased (in shares) 11,300 24,000 28,000 63,300  
Dollar value of shares that may yet be purchased under the plans $ 5,600,000 $ 5,800,000 $ 6,300,000 $ 5,600,000 $ 5,600,000
Average price paid per share (usd per share) $ 19.22 $ 19.70 $ 18.47 $ 19.07  
Publicly Announced Plan | Common Stock          
Class of Stock [Line Items]          
Shares repurchased (in shares) 11,300 24,000 28,000 63,300