Notes Payable (Credit Facility and Construction Loan Textuals) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Feb. 28, 2012
Line of Credit [Member]
Line of Credit Facility [Line Items]
Previous borrowing capacity under the credit facility		$ 350
Debt Instrument, Previous Maturity Date	Aug. 29, 2012
Debt Instrument, Maturity Date	Feb. 28, 2016
Extension of Mortgage Loans Maturity Conditions	one-year extension option upon certain conditions and with the payment of a fee
Line of credit maximum borrowing capacity	308.9	500.0
Unencumbered interest coverage ratio	2.00
Minimum consolidated fixed charge coverage ratio	1.40
Possible future minimum consolidated fixed charge coverage ratio	1.50
Leverage ratio, upper limit (percent)	60.00%
Line of Credit [Member] | Prime rate [Member]
Line of Credit Facility [Line Items]
Variable rate basis	prime rate
Line of Credit [Member] | Federal funds rate [Member]
Line of Credit Facility [Line Items]
Variable rate basis	federal funds rate
Debt Instrument, Basis Spread on Variable Rate	0.50%
Line of Credit [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Adjusted interest rate for construction loan	LIBOR
Variable rate basis	LIBOR
Debt Instrument, Basis Spread on Variable Rate	1.50%
Debt Instrument, Base Rate Spread on Variable Rate	1.00%
Construction Loans [Member]
Line of Credit Facility [Line Items]
Number of possible loan extensions	2
Period of loan extension	1 year
Debt Instrument, Maturity Date	Sep. 12, 2014
Extension of Mortgage Loans Maturity Conditions	two, one-year periods if certain conditions are met
Square footage of real estate property (square feet)	100,000
Construction Loan Maximum Borrowing Capacity	$ 15.0
Debt Instrument, Interest Rate at Period End	1.82%
Percentage of Guarantee Obligation on Mortgage Loan Maximum Exposure	25.00%
Construction Loans [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Variable rate basis	LIBOR
Debt Instrument, Basis Spread on Variable Rate	1.65%