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Fair Value of Financial Instruments (Other Investments - AVCT) (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items] |  |
Equity investments, adjusted cost basis, amount | $ 17.0 | $ 18.0
AVCT [Member] |  |
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items] |  |
Equity investment ownership percentage | 9.00% | 21.00%
Beneficial ownership of all interests percentage | 21.00% | 21.00%
Equity investment and warrants, amount paid (in dollars) | $ 5.0 |
Unrealized fair value measurement gains, net, AVCT shares | 10.1 |
Unrealized gains on AVCT convertible debentures, before tax | 1.8 |
Unrealized gains on AVCT convertible debentures, net of tax | 1.4 |
Equity investments, adjusted cost basis, amount |  | $ 2.0
AVCT [Member] | Common Stock [Member] |  |
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items] |  |
Equity securities, fair value | $ 17.0 |

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- Definition Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(3)(d)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117546-209714 + Details
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