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Investing Receivables (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Investing receivables | $ 57,493 | $ 52,279
Notes receivable from City of Huntsville [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Investing receivables | $ 54,472 | 49,258
Notes receivable from City of Huntsville [Member] | LW Redstone Company, LLC [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Stated interest rate (as a percent) | 9.95% |
Debt instrument, term | 30 years |
Other investing loans receivable [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Investing receivables | $ 3,021 | $ 3,021

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- Definition Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.3) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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