Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
Rental and other property	$ 531,936	$ 465,713	$ 405,728
Management and other fees from affiliates	11,489	6,780	4,551
Total revenues	543,425	472,493	410,279
Expenses:
Property operating, excluding real estate taxes	125,437	115,528	104,049
Real estate taxes	48,651	43,706	39,115
Depreciation	170,592	151,428	128,221
General and administrative	23,307	20,694	23,255
Cost of management and other fees	6,513	4,610	2,707
Impairment and other charges	0	0	2,302
Total expenses	374,500	335,966	299,649
Earnings from operations	168,925	136,527	110,630
Interest expense before amortization	(100,244)	(91,694)	(82,756)
Amortization expense	(11,644)	(11,474)	(4,828)
Interest and other income	13,833	17,139	27,841
Equity income (loss) from co-investments	41,745	(467)	(1,715)
Gain on remeasurement of co-investment	21,947	0	0
Loss on early retirement of debt	(5,009)	(1,163)	(10)
Income before discontinued operations	129,553	48,868	49,162
Income from discontinued operations	10,037	8,648	1,620
Net income	139,590	57,516	50,782
Net income attributable to noncontrolling interest	(14,306)	(10,446)	(14,848)
Net income attributable to controlling interest	125,284	47,070	35,934
Dividends to preferred stockholders	(5,472)	(4,753)	(2,170)
Excess of cash paid to redeem preferred stock and units over the carrying value	0	(1,949)	0
Net income available to common stockholders	$ 119,812	$ 40,368	$ 33,764
Basic:
Income before discontinued operations available to common stockholders (in dollars per share)	$ 3.15	$ 0.99	$ 1.09
Income from discontinued operations available to common stockholders (in dollars per share)	$ 0.27	$ 0.25	$ 0.05
Net income available to common stockholders (in dollars per share)	$ 3.42	$ 1.24	$ 1.14
Weighted average number of shares outstanding during the year (in shares)	35,032,491	32,541,792	29,667,064
Diluted:
Income before discontinued operations available to common stockholders (in dollars per share)	$ 3.14	$ 0.99	$ 1.09
Income from discontinued operations available to common stockholders (in dollars per share)	$ 0.27	$ 0.25	$ 0.05
Net income available to common stockholders (in dollars per share)	$ 3.41	$ 1.24	$ 1.14
Weighted average number of shares outstanding during the year (in shares)	35,124,921	32,628,714	29,734,383