Summary of Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
Revenues included in Discontinued Operations	$ 126,005	$ 120,317	$ 122,307	$ 120,378	$ 116,230	$ 113,760	$ 123,413	$ 120,526
Net income (loss) attributable to common stockholders	46,326	34,998	31,864	15,554	(37,179)	11,637	5,697	13,181
Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Nonredeemable	94	73	70	39	(10)	39	23	54
Net Income (Loss) Attributable to Common Unit Holders	46,420	35,071	31,934	15,593	(37,189)	11,676	5,720	13,235
Earnings Per Share, Basic	$ 0.50	$ 0.38	$ 0.35	$ 0.17	$ (0.41)	$ 0.13	$ 0.06	$ 0.14
Earnings Per Share, Diluted	$ 0.50	$ 0.38	$ 0.35	$ 0.17	$ (0.41)	$ 0.13	$ 0.06	$ 0.14
Scenario, Previously Reported [Member]
Revenues included in Discontinued Operations	126,005	122,110	125,842	126,088	122,002	120,013	129,767	127,389
Restatement Adjustment [Member]
Revenues included in Discontinued Operations	$ 0	$ (1,793)	$ (3,535)	$ (5,710)	$ (5,772)	$ (6,253)	$ (6,354)	$ (6,863)