Fair Values of Financial Instruments (Details) (USD $)	Apr. 25, 2013	Sep. 30, 2013 Carrying Amount	Dec. 31, 2012 Carrying Amount	Sep. 30, 2013 Fair Value	Dec. 31, 2012 Fair Value
Financial Assets [Abstract]
Cash and cash equivalents		$ 42,518,000	$ 81,856,000	$ 42,518,000	$ 81,856,000
Note receivable, net		78,800,000	0	80,000,000	0
Mortgage loan		3,523,000	0	3,523,000	0
Derivative financial instruments		1,661,000	0	1,661,000	0
Financial Liabilities [Abstract]
Mortgage notes payable		722,313,000	605,890,000	700,362,000	623,604,000
Notes payable to banks		391,000,000	262,000,000	387,961,000	254,215,000
Interest rate swap agreements		10,390,000	16,285,000	10,390,000	16,285,000
Series D Cumulative Redeemable Preferred Stock redemption amount	$ 136,300,000