Condensed Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Tenant and other receivables allowance	1,427	499
Deferred rent receivables allowance	420	216
Preferred stock, par value	0.01	0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Private Perpetual Preferred Units, Liquidation Preference Per Share	16.62	16.62
Private Perpetual Preferred Units [Member]
Private perpetual units issued	1,560,360	1,560,360
Common Class A [Member]
Common stock, par value	0.01	0.01
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	106,044,560	94,484,023
Common stock, shares outstanding	106,030,449	94,484,023
Common Class B [Member]
Common stock, par value	0.01	0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	1,161,438	1,161,438
Common stock, shares outstanding	1,122,130	1,122,130