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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. (Investments) (Details)	12 Months Ended
	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

X

- 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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration