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INVESTMENTS. (Dividends) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Dividends excluding capital gain distributions [Member] | Available-for-sale sponsored investment portfolios [Member] |  |  |
Net Investment Income [Line Items] |  |  |
Dividends | $ 8.2 | $ 8.7 | $ 18.1

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- Definition Amount of dividend income on nonoperating securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(a)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
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