Concentrations (Details) - leased_property |
12 Months Ended | ||
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Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Concentration Risk [Line Items] | |||
| Number of significant leased properties | 3 | ||
| Revenue from Contract with Customer [Member] | Customer Concentration Risk [Member] | |||
| Concentration Risk [Line Items] | |||
| Percentage of revenues | 11.00% | 12.00% | 15.00% |
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- Definition Number of Significant Leases No definition available.
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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 For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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