Note 3 - Discontinued Operations (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012 sqft		Sep. 30, 2011	Dec. 31, 2011 sqft
Number of Real Estate Properties	26			690
(in Square feet)	2,493,000	[1]		84,400,000
Real Estate Investment Property, Net	$ 7,078,206,000			$ 6,898,445,000
Real Estate Investment Property, Accumulated Depreciation	1,745,992,000			1,693,090,000
Impairment of Real Estate	37,600,000		16,700,000
Fair Value Of Real Estate	16,141,000			5,289,000
Assets Held-for-sale [Member] | Operating Properties [Member] | Impairment of Property Carrying Value [Member]
Number of Real Estate Properties	3
Assets Held-for-sale [Member] | Operating Properties [Member] | Sold [Member]
Number of Real Estate Properties	2
Assets Held-for-sale [Member] | Operating Properties [Member]
Number of Real Estate Properties	17
Assets Held-for-sale [Member] | Remaining [Member]
Number of Real Estate Properties	16
Real Estate Investment Property, Accumulated Depreciation	46,400,000
Real Estate Held-for-sale	59,100,000
Assets Held-for-sale [Member]
(in Square feet)	1,900,000
Real Estate Investment Property, Net	69,800,000
Real Estate Investment Property, Accumulated Depreciation	51,100,000
Impairment of Real Estate	4,200,000
Fair Value Of Real Estate	98,600,000
Operating Properties [Member] | Sold [Member]
Number of Real Estate Properties	3
Impairment of Property Carrying Value [Member]
Number of Real Estate Properties	3
Impairment of Real Estate	22,200,000
Fair Value Of Real Estate	$ 16,100,000

[1] Gross leasable area ("GLA")