SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 property	Mar. 31, 2012	Dec. 31, 2012
SEGMENT INFORMATION
Number of reportable segments	3
Balance Sheet
Investments in unconsolidated real estate ventures	$ 102,102		$ 106,313
Total assets	3,229,096		3,223,477
Statement of Operations
Total revenues	119,322	90,987
Operating expenses, including depreciation and amortization	72,593	58,217
Income (loss) from operations	46,729	32,770
Interest expense	(17,366)	(18,515)
Interest income	184	275
Interest income on note receivable from Preferred Operating Partnership unit holder	1,213	1,213
Equity in earnings of unconsolidated real estate ventures	2,623	2,296
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partners' interests	2,556	5,429
Income tax expense	(2,008)	(950)
Net income	33,931	22,518
Depreciation and amortization expense
Total depreciation and amortization expense	23,025	16,524
Statement of Cash Flows
Acquisition of real estate assets Property management, acquisition and development	(18,754)	(18,495)
Rental operations
Balance Sheet
Investments in unconsolidated real estate ventures	102,102		106,313
Total assets	3,002,322		2,996,453
Statement of Operations
Total revenues	102,923	75,844
Operating expenses, including depreciation and amortization	55,968	42,125
Income (loss) from operations	46,955	33,719
Interest expense	(16,980)	(17,784)
Equity in earnings of unconsolidated real estate ventures	2,623	2,296
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partners' interests	2,556	5,429
Net income	35,154	23,660
Depreciation and amortization expense
Total depreciation and amortization expense	21,531	15,529
Tenant reinsurance
Balance Sheet
Total assets	24,255		27,645
Statement of Operations
Total revenues	10,221	8,557
Operating expenses, including depreciation and amortization	1,910	1,848
Income (loss) from operations	8,311	6,709
Interest income	4	3
Income tax expense	(2,866)	(2,349)
Net income	5,449	4,363
Property management, acquisition and development
Balance Sheet
Total assets	202,519		199,379
Statement of Operations
Total revenues	6,178	6,586
Operating expenses, including depreciation and amortization	14,715	14,244
Income (loss) from operations	(8,537)	(7,658)
Interest expense	(386)	(731)
Interest income	180	272
Interest income on note receivable from Preferred Operating Partnership unit holder	1,213	1,213
Income tax expense	858	1,399
Net income	(6,672)	(5,505)
Depreciation and amortization expense
Total depreciation and amortization expense	1,494	995
Statement of Cash Flows
Acquisition of real estate assets Property management, acquisition and development	$ (18,754)	$ (18,495)