SUBSEQUENT EVENTS (Details) (USD $)	3 Months Ended		0 Months Ended	3 Months Ended												1 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Aug. 10, 2012 Subsequent Event [Member]	Jul. 31, 2012 Subsequent Event [Member]	Aug. 31, 2012 Subsequent Event [Member]	Jul. 31, 2012 Subsequent Event [Member] Prairiewood Meadows Apartments [Member]	Jul. 31, 2012 Subsequent Event [Member] Terrace on the Green Apartments [Member]	Jul. 31, 2012 Subsequent Event [Member] Candlelight Apartments [Member]	Aug. 10, 2012 Subsequent Event [Member] Williston Apartments, Williston, North Dakota [Member] acre	Aug. 01, 2012 Subsequent Event [Member] Williston Apartments, Williston, North Dakota [Member]	Aug. 31, 2012 Subsequent Event [Member] St. Cloud, MN [Member]	Aug. 10, 2012 Subsequent Event [Member] St. Cloud, MN [Member] acre	Jul. 31, 2012 Subsequent Event [Member] Sartell, Minnesota [Member] acre	Jul. 31, 2012 Subsequent Event [Member] Billings, Montana [Member] acre	Aug. 31, 2012 Subsequent Event [Member] River Ridge Apartments [Member]	Sep. 04, 2012 Subsequent Event [Member] Common Shares [Member] Dividend Declared [Member]	Sep. 04, 2012 Subsequent Event [Member] Series A Preferred Stock [Member] Dividend Declared [Member]	Sep. 04, 2012 Subsequent Event [Member] Series B Preferred Stock [Member] Dividend Declared [Member]	Aug. 07, 2012 Subsequent Event [Member] Repayment of Debt [Member]	Aug. 07, 2012 Subsequent Event [Member] Issuance of Equity [Member] Series B Cumulative Preferred Stock [Member]
Subsequent Event [Line Items]
Shares issued, shares (in shares)																				4,600,000
Shares issued (in dollars per share)																				25.00
Shares issued	$ 2,566,000	$ 549,000																		$ 111,200,000
Redemption value of preferred stock (in dollars per share)																				25.00
Preferred stock dividends, annual rate (in dollars per share)																				1.9875
Preferred stock dividends, annual rate (in hundredths)																				7.95%
Liquidation preference rate (in dollars per share)																				25.00
Liquidation preference																				115,000,000
Repayment of borrowings																			34,500,000
Borrowed amount	44,500,000																		10,000,000
Common stock, dividends, per share, declared (in dollars per share)	0.1300	0.1715														13.00
Preferred stock, dividends per share, declared (in dollars per share)																	51.56	33.12
Preferred stock, dividends per share, distribution (in dollars per share)																		49.68
Number of parcels of vacant land acquired			2
Purchase price of acquired property										823,000
Area of land (in acres)									2.6			3.8	6.5	8.9
Cash paid for acquisition of property												447,000	5,100,000	20,000,000
Number of buildings											2		2	4
Number of units						85	116	66			132		58	204	146
Number of properties sold				3
Projected revenue				2,800,000
Estimated cost of construction											$ 14,300,000				$ 24,200,000
Interest in joint venture (in hundredths)					21.00%						79.00%