Income Taxes Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Gains (Losses) on Sales of Investment Real Estate	$ 21,316,000	$ 0	$ 0
Deferred Tax Assets, Gross	930,000	273,000
Income Taxes Paid	140,000	112,000	124,000
Texas Franchise Tax [Member]
Income Taxes [Line Items]
Income Tax Expense (Benefit)	$ 140,000	$ 142,000	$ 138,000