Quarterly report pursuant to Section 13 or 15(d)

Investing Receivables (Details)

v3.8.0.1
Investing Receivables (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Investing receivables $ 58,800 $ 57,493
Notes Receivable from City of Huntsville    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Investing receivables $ 55,779 54,472
Notes Receivable from City of Huntsville | LW Redstone Company, LLC    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Stated interest rate (as a percent) 9.95%  
Other investing loans receivable    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Investing receivables $ 3,021 $ 3,021