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Equity (Dividends) (Details) - USD ($) $ in Millions | 6 Months Ended |  |
--- | --- | --- | ---
Jun. 30, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Dividends [Abstract] |  |  |
Minimum percentage of taxable income (excluding net capital gains) to be distributed in order to qualify as REIT | 90.00% |  |
Percentage of taxable income (including net capital gains) to be distributed in order to qualify as REIT | 100.00% |  |
Operating loss carryforwards |  | $ 588.0 | $ 948.8

X
- Definition Represents the minimum percentage of taxable income (excluding capital gains) to be distributed in order to qualify as REIT. + References No definition available. + Details
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- Definition Represents the percentage of taxable income (including capital gains) to be distributed in order to qualify as REIT. + References No definition available. + Details
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- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319 + Details
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