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Common Stock Common Stock (Details) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2017 | Dec. 31, 2016
Class of Stock [Line Items] |  |
Shares Issued During Period, Value, Share-based Compensation | $ 1.2 |
Sales Agency Agreements Common Stock, Shares Authorized | 200,000,000 | 200,000,000
Document Period End Date | Jun. 30, 2017 |
Shares Issued During Period, Share-based Compensation | 200,000 |
Sales Agency Agreement [Member] |  |
Class of Stock [Line Items] |  |
Shares issued |  | 1,600,000
Sales Agency Agreements Common Stock, Shares Authorized | 3,800,000 |
Common Stock Shares Authorized Under Sales Agency Agreements Remaining Shares Authorized To Sell | 2,200,000 |

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- Definition The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD. + References No definition available. + Details
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