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Fair Value Of Financial Instruments (Schedule Of Changes In Fair Value Associated With Level 3 Financial Instruments) (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Transfers, Into Level 3 |  | $ 0
Transfers, Out of Level 3 | $ 0 | (18,300,000)
Non-Agency [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning Balance | 525,000 | 1,082,000
Unrealized gains/(losses), Included in changes in net assets | (160,000) | (260,000)
Realized gains/(losses) | (7,000) | 90,000
Sales |  | (324,000)
Redemptions |  | (230,000)
Net change | (167,000) | (724,000)
Ending Balance | 358,000 | 358,000
Fixed Income Securities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning Balance | 256,000 | 273,000
Redemptions | (8,000) | (25,000)
Net change | (8,000) | (25,000)
Ending Balance | 248,000 | 248,000
Equity Securities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning Balance | 367,000 | 600,000
Unrealized gains/(losses), Included in changes in net assets | 159,000 | (74,000)
Realized gains/(losses) | (259,000) | (259,000)
Net change | (100,000) | (333,000)
Ending Balance | 267,000 | 267,000
Corporate Equity Securities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning Balance | 240,000 | 3,833,000
Transfers, Out of Level 3 |  | (3,593,000)
Net change |  | (3,593,000)
Ending Balance | 240,000 | 240,000
Equity Auction Rate Securities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning Balance | 34,621,000 | 48,689,000
Unrealized gains/(losses), Included in changes in net assets | (13,000) | 604,000
Transfers, Out of Level 3 |  | (14,685,000)
Net change | (13,000) | (14,081,000)
Ending Balance | 34,608,000 | 34,608,000
Auction Rate Municipal Securities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning Balance | 841,000 | 832,000
Unrealized gains/(losses), Included in changes in net assets | (1,000) | 8,000
Net change | (1,000) | 8,000
Ending Balance | 840,000 | 840,000
Other Investment [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning Balance | 1,240,000 | 1,240,000
Ending Balance | $ 1,240,000 | $ 1,240,000

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- Definition Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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