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Equity-Based Plans (Details) - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2015 | Sep. 30, 2013 | Jun. 30, 2013 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2013
stock offering | 10,400,000 |  | 11,100,000 |  |  |  | 700,000
Proceeds from Issuance of Common Stock | $ 271,000,000 | $ 20,000,000 |  | $ 0 | $ 0 | $ 271,000,000 |
employee stock purchase plan shares authorized |  |  |  | 625,000 |  |  |
Employee Stock Purchase Plan, Base Pay Threshold |  |  |  | 10.00% |  |  |
Employee Stock Purchase Plan, Purchased Stock Value Limitation |  |  |  | $ 25,000 |  |  |
Employee Stock Purchase Plan, Share Purchase Limitation |  |  |  | 1,500 |  |  |
Employee Stock Purchase Plan, Purchase Price |  |  |  | 95.00% |  |  |
Employee Stock Purchase Plan, Number of Available Shares |  |  |  | 339,542 |  |  |
Dividend Reinvestment and Direct Stock Purchase Plan Shares |  |  |  | 2,500,000 |  |  |
Dividend Reinvestment and Direct Stock Purchase Plan, Number of Available Shares |  |  |  | 2,470,052 |  |  |

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- Definition Represents common shares set aside, issued and available for issue related to the Dividend Reinvestment and Direct Stock Purchase Plan + References No definition available. + Details
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- Definition Employee Stock Purchase Plan, Purchase Price reflected in percentage of FMV at Purchase date. + References No definition available. + Details
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- Definition employee stock purchase plan shares authorized + References No definition available. + Details
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- Definition The cash inflow from the additional capital contribution to the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585 + Details
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