Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Per Share Dividend Payments to Common Stockholders [Line Items]
Dividends declared per common share	$ 2.86	$ 2.715	$ 2.36
Income Tax Expense (Benefit)	$ 137,000	$ 96,000	$ 82,000
Deferred Income Tax Expense (Benefit)	0	0	0
Income Taxes Paid	96,000	82,000	52,000
Taxable REIT Subsidiary [Member]
Per Share Dividend Payments to Common Stockholders [Line Items]
Income Tax Expense (Benefit)	20,000
Other Than Taxable REIT Subsidiary [Member]
Per Share Dividend Payments to Common Stockholders [Line Items]
Income Tax Expense (Benefit)	$ 117,000