SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended			36 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011 reportable_segments	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011
Segment Reporting Information [Line Items]
Number of Reportable Segments									5
Revenues	$ 38,213	$ 36,656	$ 37,845	$ 37,447	$ 36,044	$ 36,302	$ 33,997	$ 34,702	$ 150,161	$ 141,045	$ 134,445
Property operating expenses and real estate taxes									48,057	46,478	43,991
Reserve for notes receivable									0	0	1,734
Abandonment of project costs									0	0	2,487
General and administrative expenses									23,086	20,220	22,006
Income before depreciation and amortization									79,018	74,347	64,227
Depreciation and amortization									(32,986)	(28,808)	(27,612)
Interest and other finance expense									(37,109)	(40,498)	(35,632)
Real estate at cost	1,471,745				1,305,561				1,471,745	1,305,561	1,119,758	1,471,745
Total assets	1,653,319				1,524,806				1,653,319	1,524,806	1,382,464	1,653,319
Expenditures for real estate and improvements									181,498	80,520	127,322
Other interest income									276	408	642
Equity in earnings (losses) of unconsolidated affiliates									1,555	10,971	(1,529)
Impairment of investment in unconsolidated affiliate									0	0	(3,768)
Gain on debt extinguishment									1,268	0	7,057
Income tax provision									474	2,890	1,541
Gain from bargain purchase									0	33,805	0
Impairment of asset									(6,925)	0	0
Gain on sale of property									46,830	0	7,143	53,973
Income from discontinued operations									2,262	3,332	3,719
Net income									53,715	50,667	12,706
Net (income) loss attributable to noncontrolling interests									(2,160)	(20,610)	18,427
Net income attributable to Common Shareholders	7,887	4,011	30,234	9,423	7,012	5,117	12,798	5,130	51,555	30,057	31,133
Core Portfolio [Member]
Segment Reporting Information [Line Items]
Revenues									57,994	57,084	64,249
Property operating expenses and real estate taxes									17,087	17,236	19,282
Reserve for notes receivable											0
Abandonment of project costs											12
General and administrative expenses									24,226	22,439	23,983
Income before depreciation and amortization									16,681	17,409	20,972
Depreciation and amortization									(14,206)	(13,798)	(14,595)
Interest and other finance expense									(15,967)	(18,036)	(19,539)
Real estate at cost	499,872				441,714				499,872	441,714	436,071	499,872
Total assets	633,345				574,497				633,345	574,497	558,240	633,345
Expenditures for real estate and improvements									72,571	4,137	3,161
Opportunity Funds [Member]
Segment Reporting Information [Line Items]
Revenues									55,888	42,062	37,375
Property operating expenses and real estate taxes									18,952	17,671	14,874
Reserve for notes receivable											0
Abandonment of project costs											2,475
General and administrative expenses									16,678	13,588	13,593
Income before depreciation and amortization									20,258	10,803	6,433
Depreciation and amortization									(15,454)	(10,898)	(10,480)
Interest and other finance expense									(16,546)	(18,244)	(10,657)
Real estate at cost	773,562				667,179				773,562	667,179	486,032	773,562
Total assets	901,758				772,715				901,758	772,715	607,706	901,758
Expenditures for real estate and improvements									107,231	77,309	116,734
Self Storage Investments [Member]
Segment Reporting Information [Line Items]
Revenues									23,189	21,314	11,166
Property operating expenses and real estate taxes									14,435	13,107	10,985
Reserve for notes receivable											0
Abandonment of project costs											0
General and administrative expenses									0	0	0
Income before depreciation and amortization									8,754	8,207	181
Depreciation and amortization									(4,221)	(4,552)	(3,762)
Interest and other finance expense									(3,603)	(4,660)	(5,681)
Real estate at cost	213,743				210,017				213,743	210,017	208,702	213,743
Total assets	192,154				194,003				192,154	194,003	196,658	192,154
Expenditures for real estate and improvements									3,779	1,376	10,996
Notes Receivable [Member]
Segment Reporting Information [Line Items]
Revenues									11,429	19,161	19,698
Property operating expenses and real estate taxes									0	0	0
Reserve for notes receivable											1,734
Abandonment of project costs											0
General and administrative expenses									0	0	0
Income before depreciation and amortization									11,429	19,161	17,964
Depreciation and amortization									0	0	0
Interest and other finance expense									0	0	0
Real estate at cost	0				0				0	0	0	0
Total assets	59,989				89,202				59,989	89,202	125,221	59,989
Expenditures for real estate and improvements									0	0	0
Other [Member]
Segment Reporting Information [Line Items]
Revenues									25,782	22,479	23,265
Property operating expenses and real estate taxes									0	0	0
Reserve for notes receivable											0
Abandonment of project costs											0
General and administrative expenses									0	0	0
Income before depreciation and amortization									25,782	22,479	23,265
Depreciation and amortization									0	0	0
Interest and other finance expense									0	0	0
Real estate at cost	0				0				0	0	0	0
Total assets	0				0				0	0	0	0
Expenditures for real estate and improvements									0	0	0
Amounts Eliminated in Consolidation [Member]
Segment Reporting Information [Line Items]
Revenues									(24,121)	(21,055)	(21,308)
Property operating expenses and real estate taxes									(2,417)	(1,536)	(1,150)
Reserve for notes receivable											0
Abandonment of project costs											0
General and administrative expenses									(17,818)	(15,807)	(15,570)
Income before depreciation and amortization									(3,886)	(3,712)	(4,588)
Depreciation and amortization									895	440	1,225
Interest and other finance expense									(993)	442	245
Real estate at cost	(15,432)				(13,349)				(15,432)	(13,349)	(11,047)	(15,432)
Total assets	(133,927)				(105,611)				(133,927)	(105,611)	(105,361)	(133,927)
Expenditures for real estate and improvements									$ (2,083)	$ (2,302)	$ (3,569)