Summary of Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013
Revenues included in Discontinued Operations				$ 133,280	$ 126,005	$ 120,317	$ 122,307	$ 120,378
Net income (loss) attributable to common stockholders	73,515	47,942	25,482	19,389	46,326	34,998	31,864	15,554
Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Nonredeemable	134	90	53	42	94	73	70	39
Net Income (Loss) Attributable to Common Unit Holders	73,649	48,032	25,535	19,431	46,420	35,071	31,934	15,593
Earnings Per Share, Basic	$ 0.79	$ 0.52	$ 0.28	$ 0.21	$ 0.50	$ 0.38	$ 0.35	$ 0.17
Earnings Per Share, Diluted	$ 0.79	$ 0.52	$ 0.28	$ 0.21	$ 0.50	$ 0.38	$ 0.35	$ 0.17
Scenario, Previously Reported [Member]
Revenues included in Discontinued Operations	136,167	133,559	134,892		126,005	122,110	125,842	126,088
Restatement Adjustment [Member]
Revenues included in Discontinued Operations					$ 0	$ (1,793)	$ (3,535)	$ (5,710)