Real Estate and Accumulated Depreciation (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2012
Real Estate and Accumulated Depreciation [Line Items]
Amount of Encumbrance at January 31,2012	$ 5,659,523
Initial Cost to Company, Land	1,588,159
Initial Cost to Company, Buildings and Improvements	6,640,776
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,417,935
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,778,703
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	7,868,167
Gross Amount at Which Carried at Close of January 31, 2012, Total	9,646,870
Accumulated Depreciation at January 31,2012	1,526,503
Office Buildings and Hotel [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of Encumbrance at January 31,2012	2,064,588
Initial Cost to Company, Land	149,611
Initial Cost to Company, Buildings and Improvements	2,112,906
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	687,182
Gross Amount at Which Carried at Close of January 31, 2012, Land	255,252
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	2,694,447
Gross Amount at Which Carried at Close of January 31, 2012, Total	2,949,699
Accumulated Depreciation at January 31,2012	710,991
Office Buildings and Hotel [Member] | 2 Hanson Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	105,882
Initial Cost to Company, Buildings and Improvements	108,940
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	3,661
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	112,601
Gross Amount at Which Carried at Close of January 31, 2012, Total	112,601
Accumulated Depreciation at January 31,2012	16,858
Date of Construction/Acquisition	2004
Office Buildings and Hotel [Member] | 4930 Oakton [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Skokie, IL
Initial Cost to Company, Land	670
Initial Cost to Company, Buildings and Improvements	1,842
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	2,554
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,081
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	3,985
Gross Amount at Which Carried at Close of January 31, 2012, Total	5,066
Accumulated Depreciation at January 31,2012	485
Date of Construction/Acquisition	2006
Office Buildings and Hotel [Member] | Ballston Common Office Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Arlington, VA
Amount of Encumbrance at January 31,2012	44,847
Initial Cost to Company, Land	7,301
Initial Cost to Company, Buildings and Improvements	45,964
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	4,379
Gross Amount at Which Carried at Close of January 31, 2012, Land	7,301
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	50,343
Gross Amount at Which Carried at Close of January 31, 2012, Total	57,644
Accumulated Depreciation at January 31,2012	7,986
Date of Construction/Acquisition	2005
Office Buildings and Hotel [Member] | Colorado Studios [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Denver, CO
Initial Cost to Company, Land	899
Initial Cost to Company, Buildings and Improvements	1,085
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	49
Gross Amount at Which Carried at Close of January 31, 2012, Land	948
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	1,085
Gross Amount at Which Carried at Close of January 31, 2012, Total	2,033
Accumulated Depreciation at January 31,2012	522
Date of Construction/Acquisition	2007
Office Buildings and Hotel [Member] | Commerce Court [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Pittsburgh, PA
Amount of Encumbrance at January 31,2012	25,045
Initial Cost to Company, Land	3,432
Initial Cost to Company, Buildings and Improvements	20,873
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,581
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,432
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	22,454
Gross Amount at Which Carried at Close of January 31, 2012, Total	25,886
Accumulated Depreciation at January 31,2012	5,878
Date of Construction/Acquisition	2007
Office Buildings and Hotel [Member] | Edgeworth Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Richmond, VA
Amount of Encumbrance at January 31,2012	18,830
Initial Cost to Company, Land	942
Initial Cost to Company, Buildings and Improvements	29,353
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	894
Gross Amount at Which Carried at Close of January 31, 2012, Land	942
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	30,247
Gross Amount at Which Carried at Close of January 31, 2012, Total	31,189
Accumulated Depreciation at January 31,2012	3,107
Date of Construction/Acquisition	2006
Office Buildings and Hotel [Member] | Eleven MetroTech Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	61,000
Initial Cost to Company, Buildings and Improvements	41,290
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	8,835
Gross Amount at Which Carried at Close of January 31, 2012, Land	6,270
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	43,855
Gross Amount at Which Carried at Close of January 31, 2012, Total	50,125
Accumulated Depreciation at January 31,2012	18,566
Date of Construction/Acquisition	1995
Office Buildings and Hotel [Member] | Fairmont Plaza [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	San Jose, CA
Amount of Encumbrance at January 31,2012	63,524
Initial Cost to Company, Buildings and Improvements	74,624
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	10,234
Gross Amount at Which Carried at Close of January 31, 2012, Land	4,065
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	80,793
Gross Amount at Which Carried at Close of January 31, 2012, Total	84,858
Accumulated Depreciation at January 31,2012	24,512
Date of Construction/Acquisition	1998
Office Buildings and Hotel [Member] | Fifteen MetroTech Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	250,000
Initial Cost to Company, Land	3,762
Initial Cost to Company, Buildings and Improvements	163,414
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	8,488
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	175,664
Gross Amount at Which Carried at Close of January 31, 2012, Total	175,664
Accumulated Depreciation at January 31,2012	29,026
Date of Construction/Acquisition	2003
Office Buildings and Hotel [Member] | Halle Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cleveland, OH
Amount of Encumbrance at January 31,2012	11,565
Initial Cost to Company, Land	503
Initial Cost to Company, Buildings and Improvements	9,776
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	60,770
Gross Amount at Which Carried at Close of January 31, 2012, Land	4,819
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	66,230
Gross Amount at Which Carried at Close of January 31, 2012, Total	71,049
Accumulated Depreciation at January 31,2012	35,148
Date of Construction/Acquisition	1986
Office Buildings and Hotel [Member] | Harlem Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Manhattan, NY
Amount of Encumbrance at January 31,2012	32,108
Initial Cost to Company, Buildings and Improvements	31,672
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	8,362
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	40,034
Gross Amount at Which Carried at Close of January 31, 2012, Total	40,034
Accumulated Depreciation at January 31,2012	5,945
Date of Construction/Acquisition	2003
Office Buildings and Hotel [Member] | Higbee Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cleveland, OH
Amount of Encumbrance at January 31,2012	14,713
Initial Cost to Company, Land	2,452
Initial Cost to Company, Buildings and Improvements	21,261
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	58,187
Gross Amount at Which Carried at Close of January 31, 2012, Land	4,962
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	76,938
Gross Amount at Which Carried at Close of January 31, 2012, Total	81,900
Accumulated Depreciation at January 31,2012	9,804
Date of Construction/Acquisition	1990
Office Buildings and Hotel [Member] | 4901 Searle (A) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Skokie, IL
Amount of Encumbrance at January 31,2012	21,589
Initial Cost to Company, Land	837
Initial Cost to Company, Buildings and Improvements	16,227
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	4,347
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,674
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	19,737
Gross Amount at Which Carried at Close of January 31, 2012, Total	21,411
Accumulated Depreciation at January 31,2012	2,311
Date of Construction/Acquisition	2006
Office Buildings and Hotel [Member] | 8025 Lamon (P) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Skokie, IL
Amount of Encumbrance at January 31,2012	5,455
Initial Cost to Company, Land	978
Initial Cost to Company, Buildings and Improvements	6,426
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	18,627
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,957
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	24,074
Gross Amount at Which Carried at Close of January 31, 2012, Total	26,031
Accumulated Depreciation at January 31,2012	1,988
Date of Construction/Acquisition	2006
Office Buildings and Hotel [Member] | 8030 Lamon (J) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Skokie, IL
Initial Cost to Company, Land	1,325
Initial Cost to Company, Buildings and Improvements	17,376
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	19
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,325
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	17,395
Gross Amount at Which Carried at Close of January 31, 2012, Total	18,720
Accumulated Depreciation at January 31,2012	694
Date of Construction/Acquisition	2010
Office Buildings and Hotel [Member] | 8045 Lamon (Q) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Skokie, IL
Amount of Encumbrance at January 31,2012	18,045
Initial Cost to Company, Land	3,301
Initial Cost to Company, Buildings and Improvements	21,198
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	28,219
Gross Amount at Which Carried at Close of January 31, 2012, Land	6,601
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	46,117
Gross Amount at Which Carried at Close of January 31, 2012, Total	52,718
Accumulated Depreciation at January 31,2012	4,231
Date of Construction/Acquisition	2007
Office Buildings and Hotel [Member] | Johns Hopkins - 855 North Wolfe Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	East Baltimore, MD
Amount of Encumbrance at January 31,2012	70,280
Initial Cost to Company, Land	7,314
Initial Cost to Company, Buildings and Improvements	76,318
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	8,434
Gross Amount at Which Carried at Close of January 31, 2012, Land	7,314
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	84,752
Gross Amount at Which Carried at Close of January 31, 2012, Total	92,066
Accumulated Depreciation at January 31,2012	6,035
Date of Construction/Acquisition	2008
Office Buildings and Hotel [Member] | New York Times [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Manhattan, NY
Amount of Encumbrance at January 31,2012	640,000
Initial Cost to Company, Land	91,737
Initial Cost to Company, Buildings and Improvements	375,931
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	137,469
Gross Amount at Which Carried at Close of January 31, 2012, Land	141,678
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	463,459
Gross Amount at Which Carried at Close of January 31, 2012, Total	605,137
Accumulated Depreciation at January 31,2012	39,641
Date of Construction/Acquisition	2007
Office Buildings and Hotel [Member] | Nine MetroTech Center North [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	63,000
Initial Cost to Company, Buildings and Improvements	64,303
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	4,250
Gross Amount at Which Carried at Close of January 31, 2012, Land	380
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	68,173
Gross Amount at Which Carried at Close of January 31, 2012, Total	68,553
Accumulated Depreciation at January 31,2012	20,478
Date of Construction/Acquisition	1997
Office Buildings and Hotel [Member] | One MetroTech Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	169,231
Initial Cost to Company, Buildings and Improvements	212,153
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	49,375
Gross Amount at Which Carried at Close of January 31, 2012, Land	23,543
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	237,985
Gross Amount at Which Carried at Close of January 31, 2012, Total	261,528
Accumulated Depreciation at January 31,2012	94,856
Date of Construction/Acquisition	1991
Office Buildings and Hotel [Member] | One Pierrepont Plaza [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	15,864
Initial Cost to Company, Buildings and Improvements	86,863
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	91,137
Gross Amount at Which Carried at Close of January 31, 2012, Land	558
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	177,442
Gross Amount at Which Carried at Close of January 31, 2012, Total	178,000
Accumulated Depreciation at January 31,2012	95,450
Date of Construction/Acquisition	1988
Office Buildings and Hotel [Member] | Post Office Plaza (MK Ferguson) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cleveland, OH
Amount of Encumbrance at January 31,2012	15,500
Initial Cost to Company, Buildings and Improvements	57,213
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	23,363
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	80,576
Gross Amount at Which Carried at Close of January 31, 2012, Total	80,576
Accumulated Depreciation at January 31,2012	34,992
Date of Construction/Acquisition	1990
Office Buildings and Hotel [Member] | Terminal Tower [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cleveland, OH
Amount of Encumbrance at January 31,2012	35,247
Initial Cost to Company, Buildings and Improvements	29,422
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	78,546
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	107,968
Gross Amount at Which Carried at Close of January 31, 2012, Total	107,968
Accumulated Depreciation at January 31,2012	51,241
Date of Construction/Acquisition	1983
Office Buildings and Hotel [Member] | Twelve MetroTech Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	45,000
Initial Cost to Company, Buildings and Improvements	42,344
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	16,141
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,847
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	56,638
Gross Amount at Which Carried at Close of January 31, 2012, Total	58,485
Accumulated Depreciation at January 31,2012	7,646
Date of Construction/Acquisition	2004
Office Buildings and Hotel [Member] | Ten MetroTech Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	73,500
Initial Cost to Company, Land	3,680
Initial Cost to Company, Buildings and Improvements	95,234
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	5,350
Gross Amount at Which Carried at Close of January 31, 2012, Land	9,265
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	94,999
Gross Amount at Which Carried at Close of January 31, 2012, Total	104,264
Accumulated Depreciation at January 31,2012	46,948
Date of Construction/Acquisition	1992
Office Buildings and Hotel [Member] | Skylight Office Tower [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cleveland, OH
Amount of Encumbrance at January 31,2012	28,459
Initial Cost to Company, Land	2,500
Initial Cost to Company, Buildings and Improvements	32,695
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	32,592
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	67,787
Gross Amount at Which Carried at Close of January 31, 2012, Total	67,787
Accumulated Depreciation at January 31,2012	32,792
Date of Construction/Acquisition	1991
Office Buildings and Hotel [Member] | Stapleton - 3055 Roslyn [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Denver, CO
Amount of Encumbrance at January 31,2012	4,684
Initial Cost to Company, Land	225
Initial Cost to Company, Buildings and Improvements	7,523
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	728
Gross Amount at Which Carried at Close of January 31, 2012, Land	225
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	8,251
Gross Amount at Which Carried at Close of January 31, 2012, Total	8,476
Accumulated Depreciation at January 31,2012	868
Date of Construction/Acquisition	2006
Office Buildings and Hotel [Member] | Two MetroTech Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	63,249
Initial Cost to Company, Buildings and Improvements	155,280
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	(236)
Gross Amount at Which Carried at Close of January 31, 2012, Land	7,137
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	147,907
Gross Amount at Which Carried at Close of January 31, 2012, Total	155,044
Accumulated Depreciation at January 31,2012	60,275
Date of Construction/Acquisition	1990
Office Buildings and Hotel [Member] | Sheraton Station Square Hotel [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Pittsburgh, PA
Amount of Encumbrance at January 31,2012	43,812
Initial Cost to Company, Land	2,172
Initial Cost to Company, Buildings and Improvements	53,153
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	3,888
Gross Amount at Which Carried at Close of January 31, 2012, Land	2,180
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	57,033
Gross Amount at Which Carried at Close of January 31, 2012, Total	59,213
Accumulated Depreciation at January 31,2012	17,552
Date of Construction/Acquisition	1998
Office Buildings and Hotel [Member] | Miscellaneous Investments [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Various
Amount of Encumbrance at January 31,2012	8,355
Initial Cost to Company, Land	3,815
Initial Cost to Company, Buildings and Improvements	83,375
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,398
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,982
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	84,606
Gross Amount at Which Carried at Close of January 31, 2012, Total	88,588
Accumulated Depreciation at January 31,2012	16,708
Date of Construction/Acquisition Miscellaneous	Various
Office Buildings and Hotel [Member] | Richmond Office Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Richmond, VA
Amount of Encumbrance at January 31,2012	64,189
Initial Cost to Company, Land	11,766
Initial Cost to Company, Buildings and Improvements	88,632
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	4,876
Gross Amount at Which Carried at Close of January 31, 2012, Land	11,766
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	93,508
Gross Amount at Which Carried at Close of January 31, 2012, Total	105,274
Accumulated Depreciation at January 31,2012	11,098
Date of Construction/Acquisition	2007
Office Buildings and Hotel [Member] | University of Pennsylvania [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Philadelphia, PA
Amount of Encumbrance at January 31,2012	51,615
Initial Cost to Company, Buildings and Improvements	41,146
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	10,665
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	51,811
Gross Amount at Which Carried at Close of January 31, 2012, Total	51,811
Accumulated Depreciation at January 31,2012	7,350
Date of Construction/Acquisition	2004
Retail [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of Encumbrance at January 31,2012	1,735,148
Initial Cost to Company, Land	318,119
Initial Cost to Company, Buildings and Improvements	1,771,406
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	549,429
Gross Amount at Which Carried at Close of January 31, 2012, Land	399,190
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	2,239,764
Gross Amount at Which Carried at Close of January 31, 2012, Total	2,638,954
Accumulated Depreciation at January 31,2012	476,143
Retail [Member] | Promenade in Temecula [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Temecula, CA
Amount of Encumbrance at January 31,2012	167,147
Initial Cost to Company, Land	5,837
Initial Cost to Company, Buildings and Improvements	59,319
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	144,341
Gross Amount at Which Carried at Close of January 31, 2012, Land	17,428
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	192,069
Gross Amount at Which Carried at Close of January 31, 2012, Total	209,497
Accumulated Depreciation at January 31,2012	33,168
Date of Construction/Acquisition	1999
Retail [Member] | Short Pump Town Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Richmond, VA
Amount of Encumbrance at January 31,2012	154,216
Initial Cost to Company, Land	20,023
Initial Cost to Company, Buildings and Improvements	136,172
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	12,016
Gross Amount at Which Carried at Close of January 31, 2012, Land	15,124
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	153,087
Gross Amount at Which Carried at Close of January 31, 2012, Total	168,211
Accumulated Depreciation at January 31,2012	25,603
Date of Construction/Acquisition	2003
Retail [Member] | Atlantic Center Site V [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	3,782
Initial Cost to Company, Buildings and Improvements	3,238
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,485
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,047
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	3,676
Gross Amount at Which Carried at Close of January 31, 2012, Total	4,723
Accumulated Depreciation at January 31,2012	1,055
Date of Construction/Acquisition	1998
Retail [Member] | Promenade Bolingbrook [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Bolingbrook, IL
Amount of Encumbrance at January 31,2012	74,621
Initial Cost to Company, Land	20,271
Initial Cost to Company, Buildings and Improvements	95,390
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	21,504
Gross Amount at Which Carried at Close of January 31, 2012, Land	20,985
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	116,180
Gross Amount at Which Carried at Close of January 31, 2012, Total	137,165
Accumulated Depreciation at January 31,2012	14,391
Date of Construction/Acquisition	2007
Retail [Member] | Antelope Valley Mall [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Palmdale, CA
Amount of Encumbrance at January 31,2012	98,641
Initial Cost to Company, Land	1,492
Initial Cost to Company, Buildings and Improvements	58,028
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	66,615
Gross Amount at Which Carried at Close of January 31, 2012, Land	10,073
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	116,062
Gross Amount at Which Carried at Close of January 31, 2012, Total	126,135
Accumulated Depreciation at January 31,2012	36,952
Date of Construction/Acquisition	1999
Retail [Member] | Galleria at Sunset [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Henderson, NV
Amount of Encumbrance at January 31,2012	152,015
Initial Cost to Company, Land	14,965
Initial Cost to Company, Buildings and Improvements	161,893
Gross Amount at Which Carried at Close of January 31, 2012, Land	30,799
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	146,059
Gross Amount at Which Carried at Close of January 31, 2012, Total	176,858
Accumulated Depreciation at January 31,2012	34,496
Date of Construction/Acquisition	1996
Retail [Member] | Northfield at Stapleton [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Denver, CO
Amount of Encumbrance at January 31,2012	43,401
Initial Cost to Company, Land	4,830
Initial Cost to Company, Buildings and Improvements	80,687
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	83,220
Gross Amount at Which Carried at Close of January 31, 2012, Land	24,907
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	143,830
Gross Amount at Which Carried at Close of January 31, 2012, Total	168,737
Accumulated Depreciation at January 31,2012	20,919
Date of Construction/Acquisition	2005
Retail [Member] | Quebec Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Denver, CO
Amount of Encumbrance at January 31,2012	25,000
Initial Cost to Company, Land	1,616
Initial Cost to Company, Buildings and Improvements	20,615
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	7,690
Gross Amount at Which Carried at Close of January 31, 2012, Land	2,080
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	27,841
Gross Amount at Which Carried at Close of January 31, 2012, Total	29,921
Accumulated Depreciation at January 31,2012	6,077
Date of Construction/Acquisition	2002
Retail [Member] | Mall at Robinson [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Pittsburgh, PA
Amount of Encumbrance at January 31,2012	79,000
Initial Cost to Company, Land	5,475
Initial Cost to Company, Buildings and Improvements	101,086
Gross Amount at Which Carried at Close of January 31, 2012, Land	5,135
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	101,426
Gross Amount at Which Carried at Close of January 31, 2012, Total	106,561
Accumulated Depreciation at January 31,2012	27,176
Date of Construction/Acquisition	2001
Retail [Member] | Brooklyn Commons [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	22,716
Initial Cost to Company, Buildings and Improvements	23,794
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,449
Gross Amount at Which Carried at Close of January 31, 2012, Land	19,778
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	5,465
Gross Amount at Which Carried at Close of January 31, 2012, Total	25,243
Accumulated Depreciation at January 31,2012	1,126
Date of Construction/Acquisition	2004
Retail [Member] | Shops at Wiregrass [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Tampa, FL
Amount of Encumbrance at January 31,2012	118,440
Initial Cost to Company, Land	28,842
Initial Cost to Company, Buildings and Improvements	109,587
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,248
Gross Amount at Which Carried at Close of January 31, 2012, Land	35,109
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	104,568
Gross Amount at Which Carried at Close of January 31, 2012, Total	139,677
Accumulated Depreciation at January 31,2012	11,750
Date of Construction/Acquisition	2008
Retail [Member] | Quartermaster Plaza [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Philadelphia, PA
Amount of Encumbrance at January 31,2012	67,219
Initial Cost to Company, Land	36,443
Initial Cost to Company, Buildings and Improvements	32,325
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,111
Gross Amount at Which Carried at Close of January 31, 2012, Land	35,340
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	34,539
Gross Amount at Which Carried at Close of January 31, 2012, Total	69,879
Accumulated Depreciation at January 31,2012	10,542
Date of Construction/Acquisition	2004
Retail [Member] | Ballston Common Mall [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Arlington, VA
Amount of Encumbrance at January 31,2012	46,957
Initial Cost to Company, Land	170
Initial Cost to Company, Buildings and Improvements	18,069
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	66,452
Gross Amount at Which Carried at Close of January 31, 2012, Land	442
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	84,249
Gross Amount at Which Carried at Close of January 31, 2012, Total	84,691
Accumulated Depreciation at January 31,2012	41,289
Date of Construction/Acquisition	1986
Retail [Member] | Orchard Town Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Westminster, CO
Amount of Encumbrance at January 31,2012	62,856
Initial Cost to Company, Land	31,129
Initial Cost to Company, Buildings and Improvements	99,139
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	12,815
Gross Amount at Which Carried at Close of January 31, 2012, Land	31,129
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	111,954
Gross Amount at Which Carried at Close of January 31, 2012, Total	143,083
Accumulated Depreciation at January 31,2012	12,476
Date of Construction/Acquisition	2008
Retail [Member] | Avenue at Tower City Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cleveland, OH
Amount of Encumbrance at January 31,2012	26,492
Initial Cost to Company, Buildings and Improvements	174,726
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	24,366
Gross Amount at Which Carried at Close of January 31, 2012, Land	176
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	198,916
Gross Amount at Which Carried at Close of January 31, 2012, Total	199,092
Accumulated Depreciation at January 31,2012	92,337
Date of Construction/Acquisition	1990
Retail [Member] | Miscellaneous Investments [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Various
Amount of Encumbrance at January 31,2012	32,066
Initial Cost to Company, Land	16,521
Initial Cost to Company, Buildings and Improvements	42,227
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	2,119
Gross Amount at Which Carried at Close of January 31, 2012, Land	19,342
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	41,525
Gross Amount at Which Carried at Close of January 31, 2012, Total	60,867
Accumulated Depreciation at January 31,2012	7,233
Date of Construction/Acquisition Miscellaneous	Various
Retail [Member] | South Bay Galleria [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Redondo Beach, CA
Amount of Encumbrance at January 31,2012	121,117
Initial Cost to Company, Land	1,297
Initial Cost to Company, Buildings and Improvements	108,236
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	24,630
Gross Amount at Which Carried at Close of January 31, 2012, Land	8,144
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	126,019
Gross Amount at Which Carried at Close of January 31, 2012, Total	134,163
Accumulated Depreciation at January 31,2012	28,477
Date of Construction/Acquisition	1985
Retail [Member] | White Oak Village [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Richmond, VA
Amount of Encumbrance at January 31,2012	54,099
Initial Cost to Company, Land	23,738
Initial Cost to Company, Buildings and Improvements	39,758
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,467
Gross Amount at Which Carried at Close of January 31, 2012, Land	24,429
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	40,534
Gross Amount at Which Carried at Close of January 31, 2012, Total	64,963
Accumulated Depreciation at January 31,2012	5,599
Date of Construction/Acquisition	2008
Retail [Member] | Westchester's Ridge Hill [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Yonkers, NY
Amount of Encumbrance at January 31,2012	157,194
Initial Cost to Company, Land	77,892
Initial Cost to Company, Buildings and Improvements	192,147
Gross Amount at Which Carried at Close of January 31, 2012, Land	77,892
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	192,147
Gross Amount at Which Carried at Close of January 31, 2012, Total	270,039
Accumulated Depreciation at January 31,2012	3,706
Date of Construction/Acquisition	2011
Retail [Member] | Victoria Gardens [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Rancho Cucamonga, CA
Amount of Encumbrance at January 31,2012	201,375
Initial Cost to Company, Land	19,272
Initial Cost to Company, Buildings and Improvements	175,662
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	38,881
Gross Amount at Which Carried at Close of January 31, 2012, Land	10,242
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	223,573
Gross Amount at Which Carried at Close of January 31, 2012, Total	233,815
Accumulated Depreciation at January 31,2012	30,365
Date of Construction/Acquisition	2004
Retail [Member] | Tower City Parking [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cleveland, OH
Amount of Encumbrance at January 31,2012	1,508
Initial Cost to Company, Land	2,317
Initial Cost to Company, Buildings and Improvements	11,789
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	18,956
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,337
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	29,725
Gross Amount at Which Carried at Close of January 31, 2012, Total	33,062
Accumulated Depreciation at January 31,2012	12,151
Date of Construction/Acquisition	1990
Retail [Member] | Station Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Pittsburgh, PA
Amount of Encumbrance at January 31,2012	25,286
Initial Cost to Company, Land	5,989
Initial Cost to Company, Buildings and Improvements	27,519
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	19,064
Gross Amount at Which Carried at Close of January 31, 2012, Land	6,252
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	46,320
Gross Amount at Which Carried at Close of January 31, 2012, Total	52,572
Accumulated Depreciation at January 31,2012	19,255
Date of Construction/Acquisition	1994
Apartments [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of Encumbrance at January 31,2012	1,008,576
Initial Cost to Company, Land	98,667
Initial Cost to Company, Buildings and Improvements	1,304,412
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	181,324
Gross Amount at Which Carried at Close of January 31, 2012, Land	102,499
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	1,481,904
Gross Amount at Which Carried at Close of January 31, 2012, Total	1,584,403
Accumulated Depreciation at January 31,2012	331,283
Apartments [Member] | Miscellaneous Investments [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Various
Amount of Encumbrance at January 31,2012	45,035
Initial Cost to Company, Land	966
Initial Cost to Company, Buildings and Improvements	26,614
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	36,677
Gross Amount at Which Carried at Close of January 31, 2012, Land	999
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	63,258
Gross Amount at Which Carried at Close of January 31, 2012, Total	64,257
Accumulated Depreciation at January 31,2012	15,120
Date of Construction/Acquisition Miscellaneous	Various
Apartments [Member] | 100 Landsdowne Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cambridge, MA
Amount of Encumbrance at January 31,2012	45,000
Initial Cost to Company, Land	728
Initial Cost to Company, Buildings and Improvements	60,020
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	(160)
Gross Amount at Which Carried at Close of January 31, 2012, Land	819
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	59,769
Gross Amount at Which Carried at Close of January 31, 2012, Total	60,588
Accumulated Depreciation at January 31,2012	10,359
Date of Construction/Acquisition	2005
Apartments [Member] | 1251 S. Michigan [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Chicago, IL
Amount of Encumbrance at January 31,2012	9,500
Initial Cost to Company, Land	97
Initial Cost to Company, Buildings and Improvements	13,978
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	650
Gross Amount at Which Carried at Close of January 31, 2012, Land	106
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	14,619
Gross Amount at Which Carried at Close of January 31, 2012, Total	14,725
Accumulated Depreciation at January 31,2012	2,125
Date of Construction/Acquisition	2006
Apartments [Member] | American Cigar Company [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Richmond, VA
Amount of Encumbrance at January 31,2012	11,530
Initial Cost to Company, Land	1,395
Initial Cost to Company, Buildings and Improvements	23,533
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	405
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,356
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	23,977
Gross Amount at Which Carried at Close of January 31, 2012, Total	25,333
Accumulated Depreciation at January 31,2012	3,192
Date of Construction/Acquisition	2000
Apartments [Member] | Ashton Mill [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cumberland, RI
Amount of Encumbrance at January 31,2012	17,290
Initial Cost to Company, Land	2,885
Initial Cost to Company, Buildings and Improvements	33,844
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	9,137
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,242
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	42,624
Gross Amount at Which Carried at Close of January 31, 2012, Total	45,866
Accumulated Depreciation at January 31,2012	6,455
Date of Construction/Acquisition	2005
Apartments [Member] | Brookview Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Dayton, OH
Amount of Encumbrance at January 31,2012	3,294
Initial Cost to Company, Land	155
Initial Cost to Company, Buildings and Improvements	4,588
Gross Amount at Which Carried at Close of January 31, 2012, Land	155
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	4,588
Gross Amount at Which Carried at Close of January 31, 2012, Total	4,743
Accumulated Depreciation at January 31,2012	3,360
Date of Construction/Acquisition	1979
Apartments [Member] | Cameron Kinney [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Richmond, VA
Amount of Encumbrance at January 31,2012	14,000
Initial Cost to Company, Land	2,340
Initial Cost to Company, Buildings and Improvements	23,206
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	3,175
Gross Amount at Which Carried at Close of January 31, 2012, Land	2,468
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	26,253
Gross Amount at Which Carried at Close of January 31, 2012, Total	28,721
Accumulated Depreciation at January 31,2012	3,287
Date of Construction/Acquisition	2007
Apartments [Member] | Cedar Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Lansing, MI
Amount of Encumbrance at January 31,2012	3,988
Initial Cost to Company, Land	399
Initial Cost to Company, Buildings and Improvements	7,000
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	27
Gross Amount at Which Carried at Close of January 31, 2012, Land	399
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	7,027
Gross Amount at Which Carried at Close of January 31, 2012, Total	7,426
Accumulated Depreciation at January 31,2012	3,168
Date of Construction/Acquisition	1974
Apartments [Member] | Consolidated-Carolina [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Richmond, VA
Amount of Encumbrance at January 31,2012	21,290
Initial Cost to Company, Land	1,028
Initial Cost to Company, Buildings and Improvements	30,425
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,374
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,032
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	31,795
Gross Amount at Which Carried at Close of January 31, 2012, Total	32,827
Accumulated Depreciation at January 31,2012	5,892
Date of Construction/Acquisition	2003
Apartments [Member] | Cutter's Ridge at Tobacco Row [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Richmond, VA
Initial Cost to Company, Land	389
Initial Cost to Company, Buildings and Improvements	4,356
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	(130)
Gross Amount at Which Carried at Close of January 31, 2012, Land	389
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	4,226
Gross Amount at Which Carried at Close of January 31, 2012, Total	4,615
Accumulated Depreciation at January 31,2012	833
Date of Construction/Acquisition	2006
Apartments [Member] | Drake [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Philadelphia, PA
Amount of Encumbrance at January 31,2012	28,169
Initial Cost to Company, Land	1,353
Initial Cost to Company, Buildings and Improvements	38,104
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	8,097
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,353
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	46,201
Gross Amount at Which Carried at Close of January 31, 2012, Total	47,554
Accumulated Depreciation at January 31,2012	11,373
Date of Construction/Acquisition	1998
Apartments [Member] | Easthaven at the Village [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Beachwood, OH
Amount of Encumbrance at January 31,2012	26,456
Initial Cost to Company, Land	7,919
Initial Cost to Company, Buildings and Improvements	39,768
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	7,241
Gross Amount at Which Carried at Close of January 31, 2012, Land	8,081
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	46,847
Gross Amount at Which Carried at Close of January 31, 2012, Total	54,928
Accumulated Depreciation at January 31,2012	16,260
Date of Construction/Acquisition	1994
Apartments [Member] | Emerald Palms [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Miami, FL
Amount of Encumbrance at January 31,2012	24,908
Initial Cost to Company, Land	3,311
Initial Cost to Company, Buildings and Improvements	27,017
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	4,519
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,070
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	31,777
Gross Amount at Which Carried at Close of January 31, 2012, Total	34,847
Accumulated Depreciation at January 31,2012	11,737
Date of Construction/Acquisition	1996
Apartments [Member] | Forest Trace [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Lauderhill, FL
Amount of Encumbrance at January 31,2012	38,907
Initial Cost to Company, Land	4,356
Initial Cost to Company, Buildings and Improvements	41,505
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,411
Gross Amount at Which Carried at Close of January 31, 2012, Land	4,463
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	42,809
Gross Amount at Which Carried at Close of January 31, 2012, Total	47,272
Accumulated Depreciation at January 31,2012	11,856
Date of Construction/Acquisition	2000
Apartments [Member] | Foundry Lofts [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Washington, D.C.
Amount of Encumbrance at January 31,2012	47,700
Initial Cost to Company, Land	2,086
Initial Cost to Company, Buildings and Improvements	52,806
Gross Amount at Which Carried at Close of January 31, 2012, Land	2,086
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	52,806
Gross Amount at Which Carried at Close of January 31, 2012, Total	54,892
Accumulated Depreciation at January 31,2012	328
Date of Construction/Acquisition	2011
Apartments [Member] | Grand Lowry Lofts [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Denver, CO
Amount of Encumbrance at January 31,2012	18,186
Initial Cost to Company, Land	1,448
Initial Cost to Company, Buildings and Improvements	22,726
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,955
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,605
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	24,524
Gross Amount at Which Carried at Close of January 31, 2012, Total	26,129
Accumulated Depreciation at January 31,2012	4,231
Date of Construction/Acquisition	2000
Apartments [Member] | Hamel Mill Lofts [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Haverhill, MA
Amount of Encumbrance at January 31,2012	41,361
Initial Cost to Company, Land	3,974
Initial Cost to Company, Buildings and Improvements	72,902
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	497
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,974
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	73,399
Gross Amount at Which Carried at Close of January 31, 2012, Total	77,373
Accumulated Depreciation at January 31,2012	4,537
Date of Construction/Acquisition	2008
Apartments [Member] | Heritage [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	San Diego, CA
Amount of Encumbrance at January 31,2012	23,797
Initial Cost to Company, Land	7,433
Initial Cost to Company, Buildings and Improvements	42,202
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	3,280
Gross Amount at Which Carried at Close of January 31, 2012, Land	7,438
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	45,477
Gross Amount at Which Carried at Close of January 31, 2012, Total	52,915
Accumulated Depreciation at January 31,2012	12,125
Date of Construction/Acquisition	2002
Apartments [Member] | Independence Place I [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Parma Heights, OH
Amount of Encumbrance at January 31,2012	4,263
Initial Cost to Company, Land	210
Initial Cost to Company, Buildings and Improvements	6,671
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	740
Gross Amount at Which Carried at Close of January 31, 2012, Land	215
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	7,406
Gross Amount at Which Carried at Close of January 31, 2012, Total	7,621
Accumulated Depreciation at January 31,2012	3,681
Date of Construction/Acquisition	1973
Apartments [Member] | Knolls [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Orange, CA
Amount of Encumbrance at January 31,2012	19,309
Initial Cost to Company, Land	53
Initial Cost to Company, Buildings and Improvements	23,759
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	296
Gross Amount at Which Carried at Close of January 31, 2012, Land	53
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	24,055
Gross Amount at Which Carried at Close of January 31, 2012, Total	24,108
Accumulated Depreciation at January 31,2012	9,644
Date of Construction/Acquisition	1995
Apartments [Member] | Kennedy Biscuit Lofts [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cambridge, MA
Amount of Encumbrance at January 31,2012	20,600
Initial Cost to Company, Land	716
Initial Cost to Company, Buildings and Improvements	23,645
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	3,672
Gross Amount at Which Carried at Close of January 31, 2012, Land	719
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	27,314
Gross Amount at Which Carried at Close of January 31, 2012, Total	28,033
Accumulated Depreciation at January 31,2012	13,786
Date of Construction/Acquisition	1990
Apartments [Member] | Pavilion [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Chicago, IL
Amount of Encumbrance at January 31,2012	55,425
Initial Cost to Company, Land	5,250
Initial Cost to Company, Buildings and Improvements	29,505
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	11,733
Gross Amount at Which Carried at Close of January 31, 2012, Land	5,265
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	41,223
Gross Amount at Which Carried at Close of January 31, 2012, Total	46,488
Accumulated Depreciation at January 31,2012	9,991
Date of Construction/Acquisition	1992
Apartments [Member] | Midtown Towers [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Parma, OH
Amount of Encumbrance at January 31,2012	13,615
Initial Cost to Company, Land	1,215
Initial Cost to Company, Buildings and Improvements	11,091
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	10,317
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,268
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	21,355
Gross Amount at Which Carried at Close of January 31, 2012, Total	22,623
Accumulated Depreciation at January 31,2012	8,075
Date of Construction/Acquisition	1969
Apartments [Member] | Millender Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Detroit, MI
Amount of Encumbrance at January 31,2012	9,206
Initial Cost to Company, Land	1,247
Initial Cost to Company, Buildings and Improvements	16,847
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	265
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,247
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	17,112
Gross Amount at Which Carried at Close of January 31, 2012, Total	18,359
Accumulated Depreciation at January 31,2012	9,483
Date of Construction/Acquisition	1985
Apartments [Member] | Perrytown Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Pittsburgh, PA
Amount of Encumbrance at January 31,2012	4,802
Initial Cost to Company, Land	463
Initial Cost to Company, Buildings and Improvements	6,898
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1
Gross Amount at Which Carried at Close of January 31, 2012, Land	463
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	6,899
Gross Amount at Which Carried at Close of January 31, 2012, Total	7,362
Accumulated Depreciation at January 31,2012	3,566
Date of Construction/Acquisition	1973
Apartments [Member] | Independence Place II [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Parma Heights, OH
Amount of Encumbrance at January 31,2012	3,450
Initial Cost to Company, Land	498
Initial Cost to Company, Buildings and Improvements	3,931
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,403
Gross Amount at Which Carried at Close of January 31, 2012, Land	507
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	5,325
Gross Amount at Which Carried at Close of January 31, 2012, Total	5,832
Accumulated Depreciation at January 31,2012	1,301
Date of Construction/Acquisition	2003
Apartments [Member] | Parmatown Towers and Gardens [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Parma, OH
Amount of Encumbrance at January 31,2012	6,274
Initial Cost to Company, Land	330
Initial Cost to Company, Buildings and Improvements	5,059
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	7,545
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,059
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	11,875
Gross Amount at Which Carried at Close of January 31, 2012, Total	12,934
Accumulated Depreciation at January 31,2012	7,756
Date of Construction/Acquisition	1972
Apartments [Member] | Metro 417 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Los Angeles, CA
Amount of Encumbrance at January 31,2012	44,888
Initial Cost to Company, Land	8,545
Initial Cost to Company, Buildings and Improvements	67,326
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	4,094
Gross Amount at Which Carried at Close of January 31, 2012, Land	8,545
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	71,420
Gross Amount at Which Carried at Close of January 31, 2012, Total	79,965
Accumulated Depreciation at January 31,2012	10,677
Date of Construction/Acquisition	2005
Apartments [Member] | Lofts 23 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Cambridge, MA
Amount of Encumbrance at January 31,2012	6,256
Initial Cost to Company, Land	221
Initial Cost to Company, Buildings and Improvements	17,026
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	52
Gross Amount at Which Carried at Close of January 31, 2012, Land	314
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	16,985
Gross Amount at Which Carried at Close of January 31, 2012, Total	17,299
Accumulated Depreciation at January 31,2012	3,314
Date of Construction/Acquisition	2005
Apartments [Member] | One Franklintown [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Philadelphia, PA
Amount of Encumbrance at January 31,2012	38,926
Initial Cost to Company, Land	1,658
Initial Cost to Company, Buildings and Improvements	31,489
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	8,111
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,741
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	39,517
Gross Amount at Which Carried at Close of January 31, 2012, Total	41,258
Accumulated Depreciation at January 31,2012	18,371
Date of Construction/Acquisition	1988
Apartments [Member] | Sky55 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Chicago, IL
Amount of Encumbrance at January 31,2012	67,915
Initial Cost to Company, Land	3,965
Initial Cost to Company, Buildings and Improvements	80,930
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	63
Gross Amount at Which Carried at Close of January 31, 2012, Land	4,011
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	80,947
Gross Amount at Which Carried at Close of January 31, 2012, Total	84,958
Accumulated Depreciation at January 31,2012	14,265
Date of Construction/Acquisition	2006
Apartments [Member] | Town Center ( Botanica on the Green & Crescent Flats) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Denver, CO
Amount of Encumbrance at January 31,2012	32,011
Initial Cost to Company, Land	3,436
Initial Cost to Company, Buildings and Improvements	63,073
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	3,802
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,346
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	66,965
Gross Amount at Which Carried at Close of January 31, 2012, Total	70,311
Accumulated Depreciation at January 31,2012	13,186
Date of Construction/Acquisition	2004
Apartments [Member] | Lofts at 1835 Arch [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Philadelphia, PA
Amount of Encumbrance at January 31,2012	20,478
Initial Cost to Company, Land	2,076
Initial Cost to Company, Buildings and Improvements	27,430
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	11,887
Gross Amount at Which Carried at Close of January 31, 2012, Land	2,082
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	39,311
Gross Amount at Which Carried at Close of January 31, 2012, Total	41,393
Accumulated Depreciation at January 31,2012	8,834
Date of Construction/Acquisition	2001
Apartments [Member] | Wilson Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Dallas, TX
Amount of Encumbrance at January 31,2012	12,776
Initial Cost to Company, Land	2,217
Initial Cost to Company, Buildings and Improvements	16,565
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	3,306
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,937
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	20,151
Gross Amount at Which Carried at Close of January 31, 2012, Total	22,088
Accumulated Depreciation at January 31,2012	2,103
Date of Construction/Acquisition	2007
Apartments [Member] | Museum Towers [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Philadelphia, PA
Amount of Encumbrance at January 31,2012	32,400
Initial Cost to Company, Land	3,474
Initial Cost to Company, Buildings and Improvements	18,158
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	5,963
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,909
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	23,686
Gross Amount at Which Carried at Close of January 31, 2012, Total	27,595
Accumulated Depreciation at January 31,2012	7,634
Date of Construction/Acquisition	1997
Apartments [Member] | Mercantile Place on Main [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Dallas, TX
Amount of Encumbrance at January 31,2012	36,066
Initial Cost to Company, Land	8,876
Initial Cost to Company, Buildings and Improvements	75,478
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	5,018
Gross Amount at Which Carried at Close of January 31, 2012, Land	8,795
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	80,577
Gross Amount at Which Carried at Close of January 31, 2012, Total	89,372
Accumulated Depreciation at January 31,2012	9,072
Date of Construction/Acquisition	2008
Apartments [Member] | Lucky Strike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Richmond, VA
Amount of Encumbrance at January 31,2012	15,257
Initial Cost to Company, Land	1,105
Initial Cost to Company, Buildings and Improvements	34,095
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	31
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,019
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	32,212
Gross Amount at Which Carried at Close of January 31, 2012, Total	35,231
Accumulated Depreciation at January 31,2012	3,731
Date of Construction/Acquisition	2008
Apartments [Member] | Queenswood [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Corona, NY
Amount of Encumbrance at January 31,2012	28,729
Initial Cost to Company, Land	321
Initial Cost to Company, Buildings and Improvements	39,243
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	557
Gross Amount at Which Carried at Close of January 31, 2012, Land	327
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	39,794
Gross Amount at Which Carried at Close of January 31, 2012, Total	40,121
Accumulated Depreciation at January 31,2012	15,862
Date of Construction/Acquisition	1990
Apartments [Member] | Metropolitan [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Los Angeles, CA
Amount of Encumbrance at January 31,2012	38,900
Initial Cost to Company, Land	4,420
Initial Cost to Company, Buildings and Improvements	36,557
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	9,410
Gross Amount at Which Carried at Close of January 31, 2012, Land	4,458
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	45,929
Gross Amount at Which Carried at Close of January 31, 2012, Total	50,387
Accumulated Depreciation at January 31,2012	20,417
Date of Construction/Acquisition	1989
Apartments [Member] | Presidio Landmark [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	San Francisco, CA
Amount of Encumbrance at January 31,2012	56,474
Initial Cost to Company, Land	2,060
Initial Cost to Company, Buildings and Improvements	92,687
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,873
Gross Amount at Which Carried at Close of January 31, 2012, Land	2,060
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	94,560
Gross Amount at Which Carried at Close of January 31, 2012, Total	96,620
Accumulated Depreciation at January 31,2012	4,252
Date of Construction/Acquisition	2010
Apartments [Member] | Southfield [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Whitemarsh, MD
Amount of Encumbrance at January 31,2012	15,099
Initial Cost to Company, Land	3,260
Initial Cost to Company, Buildings and Improvements	8,318
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	12,621
Gross Amount at Which Carried at Close of January 31, 2012, Land	3,335
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	20,864
Gross Amount at Which Carried at Close of January 31, 2012, Total	24,199
Accumulated Depreciation at January 31,2012	5,410
Date of Construction/Acquisition	2002
Apartments [Member] | North Church Towers [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Parma Heights, OH
Amount of Encumbrance at January 31,2012	5,046
Initial Cost to Company, Land	789
Initial Cost to Company, Buildings and Improvements	4,037
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	409
Gross Amount at Which Carried at Close of January 31, 2012, Land	789
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	4,446
Gross Amount at Which Carried at Close of January 31, 2012, Total	5,235
Accumulated Depreciation at January 31,2012	634
Date of Construction/Acquisition	2009
Land Held for Development and Sale [Member] | Stapleton [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Denver, CO
Amount of Encumbrance at January 31,2012	15,775
Initial Cost to Company, Land	77,298
Gross Amount at Which Carried at Close of January 31, 2012, Land	77,298
Gross Amount at Which Carried at Close of January 31, 2012, Total	77,298
Date of Construction/Acquisition Miscellaneous	Various
Leasehold Improvements and Other Equipment [Member] | Miscellaneous Investments [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Various
Initial Cost to Company, Buildings and Improvements	10,392
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	10,392
Gross Amount at Which Carried at Close of January 31, 2012, Total	10,392
Accumulated Depreciation at January 31,2012	8,086
Date of Construction/Acquisition Miscellaneous	Various
Construction Projects [Member] | Westchester's Ridge Hill [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Yonkers, NY
Amount of Encumbrance at January 31,2012	330,533
Initial Cost to Company, Land	34,024
Initial Cost to Company, Buildings and Improvements	533,881
Gross Amount at Which Carried at Close of January 31, 2012, Land	34,024
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	533,881
Gross Amount at Which Carried at Close of January 31, 2012, Total	567,905
Date of Construction/Acquisition Miscellaneous	Various
Construction Projects [Member] | Barclays Center Arena [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	206,253
Initial Cost to Company, Buildings and Improvements	591,228
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	591,228
Gross Amount at Which Carried at Close of January 31, 2012, Total	591,228
Date of Construction/Acquisition Miscellaneous	Various
Construction Projects [Member] | Botanica Eastbridge [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Denver, CO
Initial Cost to Company, Land	631
Initial Cost to Company, Buildings and Improvements	3,639
Gross Amount at Which Carried at Close of January 31, 2012, Land	631
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	3,639
Gross Amount at Which Carried at Close of January 31, 2012, Total	4,270
Date of Construction/Acquisition Miscellaneous	Various
Construction Projects [Member] | Continental Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Dallas, TX
Amount of Encumbrance at January 31,2012	6,596
Initial Cost to Company, Land	1,950
Initial Cost to Company, Buildings and Improvements	18,628
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,950
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	18,628
Gross Amount at Which Carried at Close of January 31, 2012, Total	20,578
Date of Construction/Acquisition Miscellaneous	Various
Construction Projects [Member] | Johns Hopkins Parking Garage [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	East Baltimore, MD
Amount of Encumbrance at January 31,2012	775
Initial Cost to Company, Land	1,600
Initial Cost to Company, Buildings and Improvements	8,450
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,600
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	8,450
Gross Amount at Which Carried at Close of January 31, 2012, Total	10,050
Date of Construction/Acquisition Miscellaneous	Various
Construction Projects [Member] | The Aster Town Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Denver, CO
Initial Cost to Company, Land	335
Initial Cost to Company, Buildings and Improvements	5,448
Gross Amount at Which Carried at Close of January 31, 2012, Land	335
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	5,448
Gross Amount at Which Carried at Close of January 31, 2012, Total	5,783
Date of Construction/Acquisition Miscellaneous	Various
Construction Projects [Member] | The Yards - Boilermaker Shops [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Washington, D.C.
Initial Cost to Company, Land	24
Initial Cost to Company, Buildings and Improvements	7,550
Gross Amount at Which Carried at Close of January 31, 2012, Land	24
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	7,550
Gross Amount at Which Carried at Close of January 31, 2012, Total	7,574
Date of Construction/Acquisition Miscellaneous	Various
Development Projects [Member] | Miscellaneous Investments [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Various
Amount of Encumbrance at January 31,2012	11,568
Initial Cost to Company, Land	20,805
Initial Cost to Company, Buildings and Improvements	142,232
Gross Amount at Which Carried at Close of January 31, 2012, Land	20,805
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	142,232
Gross Amount at Which Carried at Close of January 31, 2012, Total	163,037
Date of Construction/Acquisition Miscellaneous	Various
Development Projects [Member] | Atlantic Yards [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Brooklyn, NY
Amount of Encumbrance at January 31,2012	260,627
Initial Cost to Company, Land	678,229
Gross Amount at Which Carried at Close of January 31, 2012, Land	678,229
Gross Amount at Which Carried at Close of January 31, 2012, Total	678,229
Date of Construction/Acquisition Miscellaneous	Various
Development Projects [Member] | The Yards [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Washington, D.C.
Initial Cost to Company, Land	173
Initial Cost to Company, Buildings and Improvements	65,335
Gross Amount at Which Carried at Close of January 31, 2012, Land	173
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	65,335
Gross Amount at Which Carried at Close of January 31, 2012, Total	65,508
Date of Construction/Acquisition Miscellaneous	Various
Development Projects [Member] | Colorado Science + Technology Park at Fitzsimmons [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Aurora, CO
Initial Cost to Company, Land	1,750
Initial Cost to Company, Buildings and Improvements	22,402
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,750
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	22,402
Gross Amount at Which Carried at Close of January 31, 2012, Total	24,152
Date of Construction/Acquisition Miscellaneous	Various
Development Projects [Member] | LiveWork Las Vegas [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Las Vegas, NV
Initial Cost to Company, Land	141,853
Gross Amount at Which Carried at Close of January 31, 2012, Land	141,853
Gross Amount at Which Carried at Close of January 31, 2012, Total	141,853
Date of Construction/Acquisition Miscellaneous	Various
Development Projects [Member] | The Science + Technology Park at Johns Hopkins [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	East Baltimore, MD
Initial Cost to Company, Land	5,386
Initial Cost to Company, Buildings and Improvements	16,043
Gross Amount at Which Carried at Close of January 31, 2012, Land	5,386
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	16,043
Gross Amount at Which Carried at Close of January 31, 2012, Total	21,429
Date of Construction/Acquisition Miscellaneous	Various
Development Projects [Member] | Waterfront Station [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Washington, D.C.
Initial Cost to Company, Land	559
Initial Cost to Company, Buildings and Improvements	26,824
Gross Amount at Which Carried at Close of January 31, 2012, Land	559
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	26,824
Gross Amount at Which Carried at Close of January 31, 2012, Total	27,383
Date of Construction/Acquisition Miscellaneous	Various
Construction and Development [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of Encumbrance at January 31,2012	816,352
Initial Cost to Company, Land	887,319
Initial Cost to Company, Buildings and Improvements	1,441,660
Gross Amount at Which Carried at Close of January 31, 2012, Land	887,319
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	1,441,660
Gross Amount at Which Carried at Close of January 31, 2012, Total	2,328,979
Real Estate [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of Encumbrance at January 31,2012	5,640,439
Initial Cost to Company, Land	1,531,014
Initial Cost to Company, Buildings and Improvements	6,640,776
Cost Capitalized Subsequent to Acquisition, Improvements and Carrying Costs	1,417,935
Gross Amount at Which Carried at Close of January 31, 2012, Land	1,721,558
Gross Amount at Which Carried at Close of January 31, 2012, Buildings and Improvements	7,868,167
Gross Amount at Which Carried at Close of January 31, 2012, Total	9,589,725
Accumulated Depreciation at January 31,2012	1,526,503
Land held for divestiture [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation geographical location	Various
Amount of Encumbrance at January 31,2012	19,084
Initial Cost to Company, Land	57,145
Gross Amount at Which Carried at Close of January 31, 2012, Land	57,145
Gross Amount at Which Carried at Close of January 31, 2012, Total	$ 57,145