Shareholders' Equity (Details) - USD ($)  | 
6 Months Ended | 25 Months Ended | ||
|---|---|---|---|---|
Dec. 12, 2017  | 
Jun. 30, 2018  | 
Mar. 31, 2018  | 
Feb. 24, 2016  | 
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| Class of Stock [Line Items] | ||||
| Authorized repurchase of common stock, amount | $ 50,000,000 | |||
| Treasury Stock | ||||
| Class of Stock [Line Items] | ||||
| Number of shares repurchased (in shares) | 0 | 1,675,000 | ||
| Repurchase of shares | $ 50,000,000 | $ 0 | 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition Amount of stock repurchase plan authorized. No definition available. 
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- Definition Number of shares that have been repurchased during the period and are being held in treasury. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
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