Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Buildings and improvements, accumulated depreciation	$ 117,106	$ 105,789
Deferred leasing intangibles assets, accumulated amortization	159,206	146,026
Deferred leasing intangibles liabilities, accumulated amortization	$ 7,242	$ 6,565
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common Stock, Shares, Issued	64,947,384	64,434,825
Common stock, shares outstanding	64,947,384	64,434,825
Series A Preferred Stock
Preferred stock, shares issued	2,760,000	2,760,000
Preferred stock, shares outstanding	2,760,000	2,760,000
Preferred stock, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Series B Preferred Stock
Preferred stock, shares issued	2,800,000	2,800,000
Preferred stock, shares outstanding	2,800,000	2,800,000
Preferred stock, liquidation preference (in dollars per share)	$ 25.00	$ 25.00