Derivatives (Summary Of The Fair Value Of The Equity Index Put Options) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Option Indexed to Issuer's Equity [Line Items]
Equity index put option liability	$ 20,958		$ 5,584
Net derivative gain (loss)	(15,373)	$ 3,231
Equity Index Put Option Contracts [Member] \| Derivatives Not Designated As Hedging Instruments [Member]
Option Indexed to Issuer's Equity [Line Items]
Equity index put option liability	20,958		$ 5,584
Net derivative gain (loss)	$ (15,373)	$ 3,231

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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