Condensed Consolidated Statements of Operations and Comprehensive Income (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues:
Rental and other property	$ 135,070	$ 117,226	$ 390,308	$ 343,340
Management and other fees	3,072	1,940	8,312	4,585
Total revenues	138,142	119,166	398,620	347,925
Expenses:
Property operating, excluding real estate taxes	32,951	29,642	92,421	86,426
Real estate taxes	12,358	11,208	35,470	32,619
Depreciation	43,041	37,881	125,575	111,786
General and administrative	5,276	4,966	16,440	15,626
Cost of management and other fees	1,642	1,164	4,893	3,161
Total expenses	95,268	84,861	274,799	249,618
Earnings from operations	42,874	34,305	123,821	98,307
Interest expense before amortization	(25,064)	(22,096)	(74,380)	(66,612)
Amortization expense	(2,927)	(2,936)	(8,681)	(8,527)
Interest and other income	3,003	2,741	10,869	12,357
Equity income (loss) in co-investments	3,547	317	8,998	(330)
Gain on remeasurement of co investment	0	0	21,947	0
Loss on early retirement of debt	(1,211)	(567)	(2,661)	(820)
Income from continuing operations	20,222	11,764	79,913	34,375
Income from discontinued operations	0	(679)	10,037	5,273
Net income	20,222	11,085	89,950	39,648
Net income attributable to noncontrolling interest	(2,635)	(2,031)	(9,827)	(7,882)
Net income attributable to controlling interest	17,587	9,054	80,123	31,766
Dividends to preferred stockholders	(1,368)	(1,367)	(4,104)	(3,385)
Excess of cash paid to redeem preferred stock and units over the carrying value	0	0	0	(1,949)
Net income available to common stockholders	16,219	7,687	76,019	26,432
Comprehensive income	16,462	10,742	86,034	41,765
Comprehensive income attributable to noncontrolling interest	(2,407)	(2,007)	(9,589)	(8,019)
Comprehensive income attributable to controlling interest	$ 14,055	$ 8,735	$ 76,445	$ 33,746
Basic:
Income from continuing operations (in dollars per share)	$ 0.46	$ 0.25	$ 1.92	$ 0.67
Income from discontinued operations (in dollars per share)	$ 0	$ (0.02)	$ 0.27	$ 0.15
Net income available to common stockholders (in dollars per share)	$ 0.46	$ 0.23	$ 2.19	$ 0.82
Weighted average number of shares outstanding during the period (in shares)	35,600,772	33,121,728	34,736,311	32,215,549
Diluted:
Income from continuing operations (in dollars per share)	$ 0.45	$ 0.25	$ 1.91	$ 0.67
Income from discontinued operations (in dollars per share)	$ 0	$ (0.02)	$ 0.27	$ 0.15
Net income available to common stockholders (in dollars per share)	$ 0.45	$ 0.23	$ 2.18	$ 0.82
Weighted average number of shares outstanding during the period (in shares)	35,699,666	33,209,289	34,834,076	32,304,686
Dividends per common share (in dollars per share)	$ 1.10	$ 1.04	$ 3.30	$ 3.12