SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012	Apr. 30, 2012	Apr. 30, 2011
Segment revenues and net operating income [Abstract]
Real estate revenue	$ 66,231	$ 60,546	$ 193,160	$ 179,910
Real estate expenses	26,375	24,590	76,020	74,759
Gain on Business Interruption Insurance Recovery	0	0	2,263	0
Net operating income	39,856	35,956	119,403	105,151
Depreciation/amortization	(16,300)	(15,183)	(49,028)	(44,865)
Administrative, advisory and trustee services	(2,245)	(1,659)	(6,402)	(5,944)
Other expenses	(464)	(359)	(1,496)	(1,509)
Interest expense	(15,725)	(16,411)	(48,448)	(48,389)
Interest and other income	255	279	600	645
Income from continuing operations	5,377	2,623	14,629	5,089
Income from discontinued operations	776	(102)	3,530	496
Net income	6,153	2,521	18,159	5,585
Segment Assets [Abstract]
Property owned	2,007,832		2,007,832		1,892,009
Less accumulated depreciation	(408,400)		(408,400)		(373,490)
Total property owned	1,599,432		1,599,432		1,518,519
Real Estate Held-for-sale	733		733		2,067
Cash and cash equivalents	62,302	35,502	62,302	35,502	39,989	41,191
Other investments	638		638		634
Receivables and other assets	113,963		113,963		114,569
Development in progress	20,127		20,127		27,599
Unimproved land	18,879		18,879		10,990
Total Assets	1,816,074		1,816,074		1,714,367
Multi-Family Residential [Member]
Segment revenues and net operating income [Abstract]
Real estate revenue	23,067	18,400	67,381	53,441
Real estate expenses	10,344	8,452	28,646	25,124
Gain on Business Interruption Insurance Recovery			2,263
Net operating income	12,723	9,948	40,998	28,317
Segment Assets [Abstract]
Property owned	626,763		626,763		539,783
Less accumulated depreciation	(135,673)		(135,673)		(128,834)
Total property owned	491,090		491,090		410,949
Commercial-Office [Member]
Segment revenues and net operating income [Abstract]
Real estate revenue	19,338	18,541	57,105	55,723
Real estate expenses	9,399	8,694	28,081	26,451
Gain on Business Interruption Insurance Recovery			0
Net operating income	9,939	9,847	29,024	29,272
Segment Assets [Abstract]
Property owned	611,174		611,174		605,318
Less accumulated depreciation	(133,861)		(133,861)		(121,422)
Total property owned	477,313		477,313		483,896
Commercial-Medical [Member]
Segment revenues and net operating income [Abstract]
Real estate revenue	16,207	16,610	47,051	50,299
Real estate expenses	4,129	5,220	12,395	16,709
Gain on Business Interruption Insurance Recovery			0
Net operating income	12,078	11,390	34,656	33,590
Segment Assets [Abstract]
Property owned	513,565		513,565		500,268
Less accumulated depreciation	(89,542)		(89,542)		(78,744)
Total property owned	424,023		424,023		421,524
Commercial-Industrial [Member]
Segment revenues and net operating income [Abstract]
Real estate revenue	3,853	3,596	10,890	10,597
Real estate expenses	1,095	1,078	3,050	3,178
Gain on Business Interruption Insurance Recovery			0
Net operating income	2,758	2,518	7,840	7,419
Segment Assets [Abstract]
Property owned	125,431		125,431		119,002
Less accumulated depreciation	(22,890)		(22,890)		(20,693)
Total property owned	102,541		102,541		98,309
Commercial-Retail [Member]
Segment revenues and net operating income [Abstract]
Real estate revenue	3,766	3,399	10,733	9,850
Real estate expenses	1,408	1,146	3,848	3,297
Gain on Business Interruption Insurance Recovery			0
Net operating income	2,358	2,253	6,885	6,553
Segment Assets [Abstract]
Property owned	130,899		130,899		127,638
Less accumulated depreciation	(26,434)		(26,434)		(23,797)
Total property owned	$ 104,465		$ 104,465		$ 103,841