Note 3 - Property Acquisitions, Developments and Other Investments - Acquisition of Operating Properties (Details) ft² in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2016 USD ($) ft²		Dec. 31, 2015 USD ($) ft²
Purchase Price Cash		$ 255,910	[1]	$ 712,055	[2]
Purchase Price Debt Acquired		284,732		807,591
Purchase Price Other	[3]	104,982		252,467
Purchase Price Total		$ 645,624		$ 1,772,113
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]	2,665		7,519
Jericho Atrium [Member]
Purchase Price Cash	[1]	$ 29,750
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total		$ 29,750
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[1],[4]	147
Elmont Plaza [Member]
Purchase Price Cash	[2],[5]			$ 2,400
Purchase Price Debt Acquired	[5]
Purchase Price Other	[3],[5]			3,358
Purchase Price Total	[5]			$ 5,758
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4],[5]			13
Oakwood Plaza North [Member]
Purchase Price Cash	[1],[5]	$ 53,412
Purchase Price Debt Acquired	[5]	100,000
Purchase Price Other	[3],[5]	61,588
Purchase Price Total	[5]	$ 215,000
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4],[5]	899
Garden State Pavilions [Member]
Purchase Price Cash	[2]			$ 16,300
Purchase Price Debt Acquired
Purchase Price Other	[3],[5]
Purchase Price Total				$ 16,300
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			111
Webster Square North [Member]
Purchase Price Cash	[1]	$ 8,200
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total		$ 8,200
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]	21
Kimstone [Member]
Purchase Price Cash	[2],[5]			$ 513,513
Purchase Price Debt Acquired	[5]			637,976
Purchase Price Other	[3],[5]			236,011
Purchase Price Total	[5]			$ 1,387,500
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4],[5]			5,631
Gateway Plaza [Member]
Purchase Price Cash	[1],[5]	$ 493
Purchase Price Debt Acquired	[5]	17,500
Purchase Price Other	[3],[5]
Purchase Price Total	[5]	$ 17,993
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4],[5]	97
Copperfield Village [Member]
Purchase Price Cash	[2]			$ 18,700
Purchase Price Debt Acquired				20,800
Purchase Price Other	[3]
Purchase Price Total				$ 39,500
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			165
Kentlands Market Square [Member]
Purchase Price Cash	[1]	$ 61,826
Purchase Price Debt Acquired		33,174
Purchase Price Other	[3]
Purchase Price Total		$ 95,000
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]	221
Snowden Square [Member]
Purchase Price Cash	[2]			$ 4,868
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 4,868
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			25
GEPT Portfolio [Member]
Purchase Price Cash	[1],[5]	$ 79,974
Purchase Price Debt Acquired	[5]	76,989
Purchase Price Other	[3],[5]	10,882
Purchase Price Total	[5]	$ 167,845
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4],[5]	681
Dulles Town Crossing [Member]
Purchase Price Cash	[2]			$ 4,830
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 4,830
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			9
Coulter Ave. Parcel [Member]
Purchase Price Cash	[1]	$ 6,750
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total		$ 6,750
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]	20
Flagler Park S.C. [Member]
Purchase Price Cash	[2]			$ 1,875
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 1,875
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			5
Kim Pru [Member]
Purchase Price Cash	[1],[5]	$ 15,505
Purchase Price Debt Acquired	[5]	35,700
Purchase Price Other	[3],[5]	3,218
Purchase Price Total	[5]	$ 54,423
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4],[5]	234
West Farms Parcel [Member]
Purchase Price Cash	[2]			$ 6,200
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 6,200
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			24
Hamden Mart [Member]
Purchase Price Cash	[1],[5]
Purchase Price Debt Acquired	[5]	21,369
Purchase Price Other	[3],[5]	29,294
Purchase Price Total	[5]	$ 50,663
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4],[5]	345
Milleridge Inn [Member]
Purchase Price Cash	[2]			$ 7,500
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 7,500
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]
Woodgrove Festival [Member]
Purchase Price Cash	[2]			$ 5,611
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 5,611
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			12
Montgomery Plaza [Member]
Purchase Price Cash	[2],[5]			$ 34,522
Purchase Price Debt Acquired	[5]			29,311
Purchase Price Other	[3],[5]			9,044
Purchase Price Total	[5]			$ 72,877
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			291
Coulter Avenue 125 [Member]
Purchase Price Cash	[2]			$ 1,925
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 1,925
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			6
Conroe Marketplace [Member]
Purchase Price Cash	[2],[5]			$ 18,546
Purchase Price Debt Acquired	[5]			42,350
Purchase Price Other	[3],[5]			3,104
Purchase Price Total	[5]			$ 64,000
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			289
Laurel Plaza [Member]
Purchase Price Cash	[2]			$ 1,200
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 1,200
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			4
Shops at District Heights [Member]
Purchase Price Cash	[2],[5]			$ 13,140
Purchase Price Debt Acquired	[5]			13,255
Purchase Price Other	[3],[5]			950
Purchase Price Total	[5]			$ 27,345
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			91
Village on the Park [Member]
Purchase Price Cash	[2]			$ 824
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 824
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			10
Christown Mall [Member]
Purchase Price Cash	[2]			$ 51,351
Purchase Price Debt Acquired				63,899
Purchase Price Other	[3]
Purchase Price Total				$ 115,250
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]			833
Washington St. Plaza [Member]
Purchase Price Cash	[2]			$ 8,750
Purchase Price Debt Acquired
Purchase Price Other	[3]
Purchase Price Total				$ 8,750
Purchase Price GLA (Square Foot) (Square Foot) | ft²	[4]

[1] The Company utilized $66.0 million associated with Internal Revenue Code 1031 sales proceeds.

[2] The Company utilized $89.5 million associated with Internal Revenue Code 1031 sales proceeds.

[3] Includes the Company's previously held equity interest investment.

[4] Gross leasable area ("GLA")

[5] The Company acquired from its partners their ownership interest in properties that were held in joint ventures in which the Company had noncontrolling interests. The Company evaluated these transactions pursuant to the FASB's Consolidation guidance and as a result, recognized gains on change in control of interests resulting from the fair value adjustments associated with the Company's previously held equity interests, which are included in the purchase price above in Other. The Company's previous ownership interests and gains on change in control of interests recognized as a result of these transactions are as follows (in millions):