CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
Rental income	$ 460,811	$ 422,166	$ 340,113
Residents fees and services	184,031	27,851
Total revenues	644,842	450,017	340,113
Expenses:
Depreciation	141,456	113,265	90,409
Property operating expenses	201,263	68,967	20,169
General and administrative	31,517	26,041	21,677
Acquisition related costs	9,394	12,239	3,610
Impairment of assets	3,071	1,990	5,965
Total expenses	386,701	222,502	141,830
Operating income	258,141	227,515	198,283
Interest and other income	1,117	1,451	844
Interest expense	(117,240)	(98,262)	(80,017)
Loss on early extinguishment of debt	(6,349)	(427)	(2,433)
Gain on lease terminations	375
(Loss) gain on sale of properties	(101)	21,315	109
Equity in earnings (losses) of an investee	316	139	(1)
Income before income tax expense	136,259	151,731	116,785
Income tax expense	(375)	(312)	(300)
Net income	135,884	151,419	116,485
Other comprehensive income:
Change in net unrealized gain / loss on investments	8,312	(17,383)	11,553
Share of comprehensive income of an investee	22	75	2
Comprehensive income	$ 144,218	$ 134,111	$ 128,040
Weighted average shares outstanding (in shares)	169,176	149,577	128,092
Net income per share (in dollars per share)	$ 0.80	$ 1.01	$ 0.91