SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 reportable_segments	Sep. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Number of Reportable Segments (in segments)			5
Revenues	$ 44,141	$ 35,869	$ 124,742	$ 110,301
Property operating expenses, other operating and real estate taxes	14,186	11,865	40,294	35,236
General and administrative	7,004	5,758	18,154	17,149
Income before depreciation and amortization and interest and other finance expense	22,951	18,246	66,294	57,916
Depreciation and amortization	10,365	8,183	29,326	23,960
Interest and other finance expense	9,563	9,692	26,675	27,450
Real estate at cost	1,703,318	1,428,167	1,703,318	1,428,167
Total assets	1,899,583	1,606,467	1,899,583	1,606,467	1,653,319
Expenditures for redevelopment and improvements	14,109	17,991	55,817	45,094
Acquisition of real estate	26,093	25,800	137,208	90,615
Other interest income	55	105	131	219
Equity in earnings (losses) of unconsolidated affiliates	(2,538)	3,110	1,997	3,025
Income tax (benefit) provision	(97)	(488)	1,137	(4)
(Loss) gain on debt extinguishment	0	(303)	0	1,268
Asset impairment charges				(6,925)
Income from discontinued operations	101	876	783	2,745
Gain on sale of property	5,917	0	8,585	32,498
Net income	6,655	4,647	20,652	39,340
Net (income) loss attributable to noncontrolling interests	926	(636)	(2,223)	4,328
Net income attributable to Common Shareholders	7,581	4,011	18,429	43,668
Core Portfolio
Segment Reporting Information [Line Items]
Revenues	17,917	14,277	50,193	42,820
Property operating expenses, other operating and real estate taxes	5,571	4,190	14,573	12,659
General and administrative	5,436	6,362	17,570	18,318
Income before depreciation and amortization and interest and other finance expense	6,910	3,725	18,050	11,843
Depreciation and amortization	4,712	3,547	12,954	10,475
Interest and other finance expense	4,085	3,943	11,159	12,294
Real estate at cost	634,851	499,349	634,851	499,349
Total assets	786,041	614,100	786,041	614,100
Expenditures for redevelopment and improvements	(915)	4,119	13,333	8,828
Acquisition of real estate	11,492	25,800	78,370	59,015
Opportunity Funds
Segment Reporting Information [Line Items]
Revenues	17,340	13,614	48,183	39,674
Property operating expenses, other operating and real estate taxes	5,851	4,557	17,990	13,880
General and administrative	4,948	3,438	12,436	9,443
Income before depreciation and amortization and interest and other finance expense	6,541	5,619	17,757	16,351
Depreciation and amortization	4,732	3,745	13,673	10,980
Interest and other finance expense	4,449	4,570	12,394	11,597
Real estate at cost	868,206	731,900	868,206	731,900
Total assets	993,046	875,623	993,046	875,623
Expenditures for redevelopment and improvements	14,108	13,547	40,806	34,732
Acquisition of real estate	14,601	0	58,838	31,600
Self Storage Investments
Segment Reporting Information [Line Items]
Revenues	6,729	6,141	19,204	17,148
Property operating expenses, other operating and real estate taxes	3,444	3,731	9,939	10,431
General and administrative	(3)	0	(38)	0
Income before depreciation and amortization and interest and other finance expense	3,288	2,410	9,303	6,717
Depreciation and amortization	1,188	1,070	3,440	3,089
Interest and other finance expense	827	882	2,591	2,835
Real estate at cost	217,296	211,912	217,296	211,912
Total assets	193,225	191,840	193,225	191,840
Expenditures for redevelopment and improvements	1,643	1,063	3,296	3,179
Acquisition of real estate	0	0	0	0
Notes Receivable
Segment Reporting Information [Line Items]
Revenues	1,866	1,585	6,077	9,506
Property operating expenses, other operating and real estate taxes	0	0	0	0
General and administrative	0	0	0	0
Income before depreciation and amortization and interest and other finance expense	1,866	1,585	6,077	9,506
Depreciation and amortization	0	0	0	0
Interest and other finance expense	0	0	0	0
Real estate at cost	0	0	0	0
Total assets	78,826	41,304	78,826	41,304
Expenditures for redevelopment and improvements	0	0	0	0
Acquisition of real estate	0	0	0	0
Other
Segment Reporting Information [Line Items]
Revenues	5,815	5,537	17,615	16,761
Property operating expenses, other operating and real estate taxes	0	0	0	0
General and administrative	0	0	0	0
Income before depreciation and amortization and interest and other finance expense	5,815	5,537	17,615	16,761
Depreciation and amortization	0	0	0	0
Interest and other finance expense	0	0	0	0
Real estate at cost	0	0	0	0
Total assets	0	0	0	0
Expenditures for redevelopment and improvements	0	0	0	0
Acquisition of real estate	0	0	0	0
Amounts Eliminated in Consolidation
Segment Reporting Information [Line Items]
Revenues	(5,526)	(5,285)	(16,530)	(15,608)
Property operating expenses, other operating and real estate taxes	(680)	(613)	(2,208)	(1,734)
General and administrative	(3,377)	(4,042)	(11,814)	(10,612)
Income before depreciation and amortization and interest and other finance expense	(1,469)	(630)	(2,508)	(3,262)
Depreciation and amortization	(267)	(179)	(741)	(584)
Interest and other finance expense	202	297	531	724
Real estate at cost	(17,035)	(14,994)	(17,035)	(14,994)
Total assets	(151,555)	(116,400)	(151,555)	(116,400)
Expenditures for redevelopment and improvements	(727)	(738)	(1,618)	(1,645)
Acquisition of real estate	$ 0	$ 0	$ 0	$ 0