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Summary Of Significant Accounting Policies (Change In Fair Value Of The Equity Index Put Option Contracts) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Option Indexed to Issuer's Equity [Line Items] |  |  |
Net derivative gain (loss) | $ 6,374 | $ 520 | $ 9,581
Derivatives Not Designated As Hedging Instruments [Member] | Equity Index Put Option Contracts [Member] |  |  |
Option Indexed to Issuer's Equity [Line Items] |  |  |
Net derivative gain (loss) | $ 6,374 | $ 520 | $ 9,581

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959 + Details
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