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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
	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

X

- 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

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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.

+ References

No definition available.

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