SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Segment Information
Number of reportable segments			3
Balance Sheet
Investments in real estate ventures	$ 137,997		$ 137,997		$ 140,560
Total assets	2,310,857		2,310,857		2,248,468
Statement of Operations
Total revenues	78,040	68,777	152,521	136,364
Operating expenses, including depreciation and amortization	52,188	45,971	102,639	92,695
Income (loss) from operations	25,852	22,806	49,882	43,669
Interest expense	(16,701)	(16,649)	(33,543)	(34,327)
Interest income	189	211	371	536
Interest income on note receivable from Preferred Operating Partnership unit holder	1,212	1,212	2,425	2,425
Equity in earnings of real estate ventures	2,376	1,559	4,187	3,060
Income tax expense	(411)	(1,214)	(665)	(2,259)
Net income (loss)	12,517	7,925	22,657	13,104
Depreciation and amortization expense
Total depreciation and amortization expense	14,092	12,202	27,677	24,621
Statement of Cash Flows
Acquisition of real estate assets			(82,071)	(16,460)
Development and construction of real estate assets			(4,494)	(18,306)
Property management, acquisition and development
Balance Sheet
Total assets	350,243		350,243		400,910
Statement of Operations
Total revenues	6,144	5,653	12,111	11,205
Operating expenses, including depreciation and amortization	14,854	11,855	27,536	23,422
Income (loss) from operations	(8,710)	(6,202)	(15,425)	(12,217)
Interest expense	(823)	(790)	(1,605)	(1,577)
Interest income	187	209	366	531
Interest income on note receivable from Preferred Operating Partnership unit holder	1,212	1,212	2,425	2,425
Net income (loss)	(8,134)	(5,571)	(14,239)	(10,838)
Depreciation and amortization expense
Total depreciation and amortization expense	852	484	1,627	925
Statement of Cash Flows
Acquisition of real estate assets			(82,071)	(16,460)
Development and construction of real estate assets			(4,494)	(18,306)
Rental operations
Balance Sheet
Investments in real estate ventures	137,997		137,997		140,560
Total assets	1,939,044		1,939,044		1,831,150
Statement of Operations
Total revenues	64,300	56,786	125,790	112,929
Operating expenses, including depreciation and amortization	35,952	32,659	72,106	66,593
Income (loss) from operations	28,348	24,127	53,684	46,336
Interest expense	(15,878)	(15,859)	(31,938)	(32,750)
Equity in earnings of real estate ventures	2,376	1,559	4,187	3,060
Net income (loss)	14,846	9,827	25,933	16,646
Depreciation and amortization expense
Total depreciation and amortization expense	13,240	11,718	26,050	23,696
Tenant reinsurance
Balance Sheet
Total assets	21,570		21,570		16,408
Statement of Operations
Total revenues	7,596	6,338	14,620	12,230
Operating expenses, including depreciation and amortization	1,382	1,457	2,997	2,680
Income (loss) from operations	6,214	4,881	11,623	9,550
Interest income	2	2	5	5
Income tax expense	(411)	(1,214)	(665)	(2,259)
Net income (loss)	$ 5,805	$ 3,669	$ 10,963	$ 7,296