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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. (Investments) (Details) | 12 Months Ended
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Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Duration of fund holding unrealized loss between quarter-ends generally presumed to represent other than temporary impairment | 6 months

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- Definition The period of time between quarter ends after which available-for-sale equity securities in a continuous unrealized loss position will generally be considered other than temporarily impaired under the company's impairment policy. + References No definition available. + Details
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Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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Balance Type: | na
Period Type: | duration