ACQUISITIONS, DEVELOPMENTS PLACED IN SERVICE AND DISPOSITIONS, Property Dispositions (Details) $ in Thousands			3 Months Ended		6 Months Ended	9 Months Ended
		Jan. 29, 2016 USD ($) Property	Jan. 31, 2016 USD ($) ft² Property	Jan. 31, 2015 USD ($) ft² Property Unit	Jan. 31, 2016 ft² Property	Jan. 31, 2016 USD ($) ft²	Jan. 31, 2015 USD ($) ft² Unit
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Price			$ 3,500	$ 10,000		$ 504,914	$ 27,619
Book Value and Sales Cost						442,932	28,412
Gain/(Loss)						$ 61,982	$ (793)
Office Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | Property				1	48
Number of properties transferred | Property		9
Estimated fair value of properties transferred		$ 89,300
Retail Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | Property			3	1	17
Multifamily [Member] | 83 unit - Lancaster - St. Cloud, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed							Sep. 22, 2014
Sales Price							$ 4,451
Book Value and Sales Cost							3,033
Gain/(Loss)							$ 1,418
Units | Unit				83			83
Industrial [Member] | 198,600 sq ft Eagan 2785 & 2795 - Eagan, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed							Jul. 15, 2014
Sales Price							$ 3,600
Book Value and Sales Cost							5,393
Gain/(Loss)							$ (1,793)
Area of real estate property | ft²				198,600			198,600
Other [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Price							$ 18,898
Book Value and Sales Cost							19,316
Gain/(Loss)							$ (418)
Other [Member] | 117,144 sq ft Thresher Square - Minneapolis, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed						May 18, 2015
Sales Price						$ 7,000
Book Value and Sales Cost						7,175
Gain/(Loss)						$ (175)
Area of real estate property | ft²			117,144		117,144	117,144
Other [Member] | 2,549,222 sq ft Office Sale Portfolio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed	[1]					Aug. 03, 2015
Sales Price	[1]					$ 250,000
Book Value and Sales Cost	[1]					231,537
Gain/(Loss)	[1]					$ 18,463
Area of real estate property | ft²	[1]		2,549,222		2,549,222	2,549,222
Other [Member] | 420,216 sq ft Mendota Office Center Portfolio - Mendota Heights, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed	[2]					Aug. 12, 2015
Sales Price	[2]					$ 40,000
Book Value and Sales Cost	[2]					41,574
Gain/(Loss)	[2]					$ (1,574)
Area of real estate property | ft²	[2]		420,216		420,216	420,216
Other [Member] | 1,027,208 sq ft Retail Sale Portfolio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed	[3]					Sep. 30, 2015
Sales Price	[3]					$ 78,960
Book Value and Sales Cost	[3]					71,913
Gain/(Loss)	[3]					$ 7,047
Area of real estate property | ft²	[3]		1,027,208		1,027,208	1,027,208
Other [Member] | 48,700 sq ft Eden Prairie 6101 Blue Circle Drive - Eden Prairie, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed						Oct. 19, 2015
Sales Price						$ 2,900
Book Value and Sales Cost						2,928
Gain/(Loss)						$ (28)
Area of real estate property | ft²			48,700		48,700	48,700
Other [Member] | 8,526 sq ft Burnsville I Strip Center - Burnsville, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed						Dec. 23, 2015
Sales Price						$ 1,300
Book Value and Sales Cost						913
Gain/(Loss)						$ 387
Area of real estate property | ft²			8,526		8,526	8,526
Other [Member] | 4,800 sq ft Pine City C-Store - Pine City, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed						Jan. 08, 2016
Sales Price						$ 300
Book Value and Sales Cost						355
Gain/(Loss)						$ (55)
Area of real estate property | ft²			4,800		4,800	4,800
Other [Member] | 11,003 sq ft Minot Plaza - Minot, ND [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed						Jan. 19, 2016
Sales Price						$ 1,854
Book Value and Sales Cost						393
Gain/(Loss)						$ 1,461
Area of real estate property | ft²			11,003		11,003	11,003
Other [Member] | 937,518 sq ft 9-Building Office Portfolio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed	[4],[5]					Jan. 29, 2016
Sales Price	[4]					$ 122,600
Book Value and Sales Cost	[4]					86,144
Gain/(Loss)	[4]					$ 36,456
Area of real estate property | ft²	[4],[5]		937,518		937,518	937,518
Other [Member] | 73,338 sq ft Dewey Hill - Edina, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed							May 19, 2014
Sales Price							$ 3,100
Book Value and Sales Cost							3,124
Gain/(Loss)							$ (24)
Area of real estate property | ft²				73,338			73,338
Other [Member] | 25,644 sq ft Weston Retail - Weston, WI [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed							Jul. 28, 2014
Book Value and Sales Cost							$ 1,176
Gain/(Loss)							$ (1,176)
Area of real estate property | ft²				25,644			25,644
Other [Member] | 74,568 sq ft Wirth Corporate Center - Golden Valley, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed							Aug. 29, 2014
Sales Price							$ 4,525
Book Value and Sales Cost							4,695
Gain/(Loss)							$ (170)
Area of real estate property | ft²				74,568			74,568
Other [Member] | 52,000 sq ft Kalispell Retail - Kalispell, MT [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed							Oct. 15, 2014
Sales Price							$ 1,230
Book Value and Sales Cost							1,229
Gain/(Loss)							$ 1
Area of real estate property | ft²				52,000			52,000
Other [Member] | 34,226 sq ft Fargo Express Center & SC Pad - Fargo, ND [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed							Nov. 18, 2014
Sales Price							$ 2,843
Book Value and Sales Cost							2,211
Gain/(Loss)							$ 632
Area of real estate property | ft²				34,226			34,226
Other [Member] | 79,297 sq ft Northgate I - Maple Grove, MN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed							Dec. 01, 2014
Sales Price							$ 7,200
Book Value and Sales Cost							6,881
Gain/(Loss)							$ 319
Area of real estate property | ft²				79,297			79,297
Unimproved Land [Member] | Kalispell Unimproved - Kalispell, MT [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date Disposed							Oct. 15, 2014
Sales Price							$ 670
Book Value and Sales Cost							670
Gain/(Loss)							$ 0

[1] The properties included in this portfolio disposition are: 610 Business Center, 7800 West Brown Deer Road, Ameritrade, Barry Pointe Office Park, Benton Business Park, Brenwood, Brook Valley I, Crosstown Centre, Golden Hills Office Center, Granite Corporate Center, Great Plains, Highlands Ranch I, Highlands Ranch II, Interlachen Corporate Center, Intertech Building, Minnesota National Bank, Northpark Corporate Center, Omaha 10802 Farnam Dr, Plaza VII, Plymouth 5095 Nathan Lane, Prairie Oak Business Center, Rapid City 900 Concourse Drive, Spring Valley IV, Spring Valley V, Spring Valley X, Spring Valley XI, Superior Office Building, TCA Building, Three Paramount Plaza, UHC Office, US Bank Financial Center, Wells Fargo Center, West River Business Park and Westgate.

[2] The properties included in this portfolio disposition are: Mendota Office Center I, Mendota Office Center II, Mendota Office Center III, Mendota Office Center IV and American Corporate Center.

[3] The properties included in this portfolio disposition are: Champlin South Pond, Chan West Village, Duluth 4615 Grand, Duluth Denfeld Retail, Forest Lake Auto, Forest Lake Westlake Center, Grand Forks Medpark Mall, Jamestown Buffalo Mall, Jamestown Business Center, Lakeville Strip Center, Monticello C Store & vacant land, Omaha Barnes & Noble, Pine City Evergreen Square, Rochester Maplewood Square and St. Cloud Westgate.

[4] On January 29, 2016, we transferred ownership of nine properties to the mortgage lender on a $122.6 million non-recourse loan and removed the debt obligation and accrued interest from our balance sheet. The properties had an estimated fair value of $89.3 million on the transfer date. Upon completion of this transfer, we recognized a gain on extinguishment of debt of $36.5 million, representing the difference between the loan and accrued interest payable extinguished over the carrying value of the properties, cash, accounts payable and accounts receivable transferred as of the transfer date and related closing costs.

[5] The properties included in this portfolio disposition are: Corporate Center West, Farnam Executive Center, Flagship Corporate Center, Gateway Corporate Center, Miracle Hills One, Pacific Hills, Riverport, Timberlands, and Woodlands Plaza IV.