| Investing Receivables - Components of Investing Receivables (Details) - Investing Receivables - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | 
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| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||
| Amortized cost basis | $ 83,889 | $ 87,415 | ||
| Allowance for credit losses | (2,377) | (2,794) | $ (1,599) | $ (2,851) | 
| Investing receivables, net | 81,512 | 84,621 | ||
| Notes receivable from the City of Huntsville | ||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||
| Amortized cost basis | 77,022 | 69,703 | ||
| Other investing loans receivable | ||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||
| Amortized cost basis | $ 6,867 | $ 17,712 | 
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- Definition 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. No definition available. 
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- Definition Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease. Reference 1: http://www.xbrl.org/2003/role/exampleRef 
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- Definition Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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