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Investing Receivables (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Investing Receivables |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Notes receivable, fair value disclosure | $ 73.0 | $ 74.0
Notes receivable from the City of Huntsville | LW Redstone Company, LLC |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Interest rate | 9.95% |
Note receivable term | 30 years |
Other investing loans receivable |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Interest rate | 8.00% |
Investing Receivables |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Accrued interest receivable, net of allowance for credit losses | $ 4.8 | $ 4.7

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