Cash Equivalents And Restricted Cash And Securities (Summary Of Cash Equivalents And Restricted Securities) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash Equivalents, Cost Basis	$ 63,877	$ 34,294	$ 41,075	$ 42,236
Cost Basis	1,972	2,000
Restricted Securities, Cost Basis	494	528
Unrealized Holding Gains (Losses)
Estimated Market Value	1,972	2,000
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash Equivalents, Cost Basis	1,478	1,472
Restricted Securities, Cost Basis	494	528
Unrealized Holding Gains (Losses)
Cash Equivalents, Estimated Market Value	1,478	1,472
Restricted Securities, Estimated Market Value	$ 494	$ 528

Fair value portion of all restricted cash.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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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.

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Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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The aggregate value of all restricted investments.

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This element represents the current portion of investments which are not defined as or included in marketable (debt, equity, or other) securities that are pledged or subject to withdrawal restrictions.

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Amount of unrealized gain (loss) recognized in the income statement on unsold other securities.

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