Schedule III - REAL ESTATE AND ACCUMLATED DEPRECIATION (Details)-K (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	$ 1,993,470,000
Initial Cost
Land	2,386,428,000
Buildings and Improvements	984,767,000
Costs Capitalized Subsequent to Acquisition
Land	(428,154,000)
Buildings and Improvements	1,173,515,000
Gross Amounts at Which Carried at Close of Period
Land	1,958,273,000
Buildings and Improvements	2,158,282,000
Total	4,116,556,000	3,024,833,000	2,746,596,000	2,589,730,000
Accumulated Depreciation	157,182,000	111,728,000	112,491,000	91,605,000
Aggregate cost of land, building and improvements for federal income tax purposes	3,500,000,000
Site in Pocatello Idaho [Member]
Initial Cost
Land	740,000
Buildings and Improvements	2,060,000
Costs Capitalized Subsequent to Acquisition
Land	(740,000)
Buildings and Improvements	(1,381,000)
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	679,000
Total	679,000
Allentowne [Member]
Initial Cost
Land	25,575,000
Costs Capitalized Subsequent to Acquisition
Land	(25,575,000)
Buildings and Improvements	25,475,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	25,475,000
Total	25,475,000
Anaha Condominiums [Member]
Initial Cost
Buildings and Improvements	47,783,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	47,783,000
Total	47,783,000
Bridgeland [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	15,884,000
Initial Cost
Land	257,222,000
Costs Capitalized Subsequent to Acquisition
Land	157,571,000
Buildings and Improvements	3,523,000
Gross Amounts at Which Carried at Close of Period
Land	414,793,000
Buildings and Improvements	3,523,000
Total	418,316,000
Accumulated Depreciation	599,000
Bridges at Mint Hill L L C [Member]
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	21,097,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	21,097,000
Total	21,097,000
Century Plaza [Member]
Initial Cost
Land	3,164,000
Buildings and Improvements	28,514,000
Costs Capitalized Subsequent to Acquisition
Land	(3,164,000)
Buildings and Improvements	(24,241,000)
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	4,273,000
Total	4,273,000
Circle T
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	40,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	40,000
Total	40,000
Columbia Corporate Center 70 [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	20,000,000
Initial Cost
Land	1,281,000
Buildings and Improvements	14,523,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	6,256,000
Gross Amounts at Which Carried at Close of Period
Land	1,281,000
Buildings and Improvements	20,779,000
Total	22,060,000
Accumulated Depreciation	1,612,000
Columbia Offices [Member]
Initial Cost
Land	1,575,000
Buildings and Improvements	28,447,000
Costs Capitalized Subsequent to Acquisition
Land	23,404,000
Buildings and Improvements	83,493,000
Gross Amounts at Which Carried at Close of Period
Land	24,979,000
Buildings and Improvements	111,940,000
Total	136,919,000
Accumulated Depreciation	12,517,000
Columbia Regional Building [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	20,513,000
Initial Cost
Buildings and Improvements	28,865,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	28,865,000
Total	28,865,000
Accumulated Depreciation	1,206,000
Conroe, Texas
Initial Cost
Land	99,284,000
Gross Amounts at Which Carried at Close of Period
Land	99,284,000
Total	99,284,000
Cottonwood Mall [Member]
Initial Cost
Land	7,613,000
Buildings and Improvements	42,987,000
Costs Capitalized Subsequent to Acquisition
Land	(7,613,000)
Buildings and Improvements	(22,271,000)
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	20,716,000
Total	20,716,000
Cottonwood Square [Member]
Initial Cost
Land	1,558,000
Buildings and Improvements	4,339,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	913,000
Gross Amounts at Which Carried at Close of Period
Land	1,558,000
Buildings and Improvements	5,252,000
Total	6,810,000
Accumulated Depreciation	1,624,000
Creekside Park Village Center [Member]
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	15,054,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	15,054,000
Total	15,054,000
Shops at Summerlin Centre [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	229,153,000
Costs Capitalized Subsequent to Acquisition
Land	17,248,000
Buildings and Improvements	339,399,000
Gross Amounts at Which Carried at Close of Period
Land	17,248,000
Buildings and Improvements	339,399,000
Total	356,647,000
Accumulated Depreciation	2,146,000
Elk Grove Promenade [Member]
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	8,412,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	8,412,000
Total	8,412,000
Accumulated Depreciation	4,000
Hughes Landing Hotel [Member]
Initial Cost
Buildings and Improvements	6,752,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	6,752,000
Total	6,752,000
Hughes Landing Retail [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	17,424,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	26,320,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	26,320,000
Total	26,320,000
One Hughes Landing [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	52,000,000
Costs Capitalized Subsequent to Acquisition
Land	1,678,000
Buildings and Improvements	35,062,000
Gross Amounts at Which Carried at Close of Period
Land	1,678,000
Buildings and Improvements	35,062,000
Total	36,741,000
Accumulated Depreciation	1,626,000
Two Hughes Landing [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	19,992,000
Costs Capitalized Subsequent to Acquisition
Land	2,109,000
Buildings and Improvements	34,941,000
Gross Amounts at Which Carried at Close of Period
Land	2,109,000
Buildings and Improvements	34,941,000
Total	37,050,000
Accumulated Depreciation	296,000
Three Hughes Landing [Member]
Initial Cost
Buildings and Improvements	13,008,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	13,008,000
Total	13,008,000
1725-35 Hughes Landing Boulevard [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	47,513,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	84,599,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	84,599,000
Total	84,599,000
Kendall Town Center [Member]
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	18,579,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	18,579,000
Total	18,579,000
1701 Lake Robbins
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	4,600,000
Initial Cost
Land	1,663,000
Buildings and Improvements	3,725,000
Gross Amounts at Which Carried at Close of Period
Land	1,663,000
Buildings and Improvements	3,725,000
Total	5,388,000
Accumulated Depreciation	39,000
Lake Woodlands Drive 2201 [Member]
Initial Cost
Land	3,755,000
Gross Amounts at Which Carried at Close of Period
Land	3,755,000
Total	3,755,000
One Lakes Edge [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	40,787,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	64,800,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	64,800,000
Total	64,800,000
Lakemoor Volo Land [Member]
Initial Cost
Land	320,000
Costs Capitalized Subsequent to Acquisition
Land	(320,000)
Buildings and Improvements	321,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	321,000
Total	321,000
Landmark Mall [Member]
Initial Cost
Land	28,396,000
Buildings and Improvements	67,235,000
Costs Capitalized Subsequent to Acquisition
Land	(19,408,000)
Buildings and Improvements	(37,427,000)
Gross Amounts at Which Carried at Close of Period
Land	8,988,000
Buildings and Improvements	29,808,000
Total	38,796,000
Accumulated Depreciation	8,118,000
Maryland [Member]
Initial Cost
Land	457,552,000
Costs Capitalized Subsequent to Acquisition
Land	(397,669,000)
Buildings and Improvements	6,854,000
Gross Amounts at Which Carried at Close of Period
Land	59,883,000
Buildings and Improvements	6,854,000
Total	66,738,000
Accumulated Depreciation	106,000
Millennium Waterway Apartments
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	55,584,000
Initial Cost
Land	15,917,000
Buildings and Improvements	56,002,000
Gross Amounts at Which Carried at Close of Period
Land	15,917,000
Buildings and Improvements	56,002,000
Total	71,919,000
Accumulated Depreciation	5,810,000
New Trails 9303 [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	13,074,000
Initial Cost
Land	1,929,000
Buildings and Improvements	11,915,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	1,959,000
Gross Amounts at Which Carried at Close of Period
Land	1,929,000
Buildings and Improvements	13,874,000
Total	15,803,000
Accumulated Depreciation	1,513,000
Wacker110N [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	29,000,000
Initial Cost
Buildings and Improvements	29,035,000
Costs Capitalized Subsequent to Acquisition
Land	12,249,000
Buildings and Improvements	5,461,000
Gross Amounts at Which Carried at Close of Period
Land	12,249,000
Buildings and Improvements	34,496,000
Total	46,745,000
Accumulated Depreciation	13,366,000
Riverwalk Marketplace
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	47,118,000
Initial Cost
Buildings and Improvements	94,513,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	(1,896,000)
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	92,617,000
Total	92,617,000
Accumulated Depreciation	4,391,000
Park West [Member]
Initial Cost
Land	16,526,000
Buildings and Improvements	77,548,000
Costs Capitalized Subsequent to Acquisition
Land	1,201,000
Buildings and Improvements	925,000
Gross Amounts at Which Carried at Close of Period
Land	17,727,000
Buildings and Improvements	78,473,000
Total	96,199,000
Accumulated Depreciation	20,224,000
80 South Street [Member]
Initial Cost
Buildings and Improvements	144,015,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	144,015,000
Total	144,015,000
South Street Seaport
Initial Cost
Buildings and Improvements	7,884,000
Costs Capitalized Subsequent to Acquisition
Land	15,913,000
Buildings and Improvements	100,630,000
Gross Amounts at Which Carried at Close of Period
Land	15,913,000
Buildings and Improvements	108,514,000
Total	124,427,000
Accumulated Depreciation	520,000
Summerlin [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	22,389,000
Initial Cost
Land	990,179,000
Costs Capitalized Subsequent to Acquisition
Land	(128,520,000)
Buildings and Improvements	987,000
Gross Amounts at Which Carried at Close of Period
Land	861,659,000
Buildings and Improvements	987,000
Total	862,646,000
Accumulated Depreciation	440,000
3831 Technology Forest [Member]
Initial Cost
Land	514,000
Buildings and Improvements	14,194,000
Gross Amounts at Which Carried at Close of Period
Land	514,000
Buildings and Improvements	14,194,000
Total	14,708,000
Accumulated Depreciation	21,000
The Club at Carlton Woods [Member]
Initial Cost
Land	13,796,000
Buildings and Improvements	457,000
Costs Capitalized Subsequent to Acquisition
Land	393,000
Buildings and Improvements	2,439,000
Gross Amounts at Which Carried at Close of Period
Land	14,189,000
Buildings and Improvements	2,896,000
Total	17,084,000
Accumulated Depreciation	394,000
The Metropolitan Downtown Columbia Project [Member]
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	1,484,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	1,484,000
Total	1,484,000
Woodlands Properties [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	176,663,000
Initial Cost
Land	267,996,000
Buildings and Improvements	9,814,000
Costs Capitalized Subsequent to Acquisition
Land	(57,180,000)
Buildings and Improvements	118,000
Gross Amounts at Which Carried at Close of Period
Land	210,816,000
Buildings and Improvements	9,932,000
Total	220,749,000
Accumulated Depreciation	1,378,000
Woodlands Parking Garages [Member]
Initial Cost
Land	5,857,000
Costs Capitalized Subsequent to Acquisition
Land	689,000
Buildings and Improvements	6,303,000
Gross Amounts at Which Carried at Close of Period
Land	6,546,000
Buildings and Improvements	6,303,000
Total	12,848,000
Accumulated Depreciation	184,000
Resort and Conference Center [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	76,027,000
Initial Cost
Land	13,258,000
Buildings and Improvements	37,983,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	71,345,000
Gross Amounts at Which Carried at Close of Period
Land	13,258,000
Buildings and Improvements	109,328,000
Total	122,586,000
Accumulated Depreciation	4,022,000
Waiea Condominiums [Member]
Initial Cost
Buildings and Improvements	30,555,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	30,555,000
Total	30,555,000
Ward Centers [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	238,716,000
Initial Cost
Land	164,007,000
Buildings and Improvements	89,321,000
Costs Capitalized Subsequent to Acquisition
Land	(21,157,000)
Buildings and Improvements	189,259,000
Gross Amounts at Which Carried at Close of Period
Land	142,850,000
Buildings and Improvements	278,580,000
Total	421,430,000
Accumulated Depreciation	52,551,000
Ward Workforce Housing [Member]
Initial Cost
Buildings and Improvements	5,114,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	5,114,000
Total	5,114,000
Waterway Garage Retail [Member]
Initial Cost
Land	1,342,000
Buildings and Improvements	4,255,000
Costs Capitalized Subsequent to Acquisition
Land	(1,000)
Buildings and Improvements	1,106,000
Gross Amounts at Which Carried at Close of Period
Land	1,341,000
Buildings and Improvements	5,361,000
Total	6,702,000
Accumulated Depreciation	548,000
Waterway Square 3 [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	52,000,000
Initial Cost
Land	748,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	42,214,000
Gross Amounts at Which Carried at Close of Period
Land	748,000
Buildings and Improvements	42,214,000
Total	42,962,000
Accumulated Depreciation	3,162,000
Waterway 4 [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	38,289,000
Initial Cost
Land	1,430,000
Buildings and Improvements	51,553,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	6,748,000
Gross Amounts at Which Carried at Close of Period
Land	1,430,000
Buildings and Improvements	58,301,000
Total	59,731,000
Accumulated Depreciation	7,005,000
Waterway Square Hotel [Member]
Initial Cost
Buildings and Improvements	22,473,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	22,473,000
Total	22,473,000
Waterway Square 2025 [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	14,330,000
Initial Cost
Land	2,346,000
Buildings and Improvements	8,871,000
Costs Capitalized Subsequent to Acquisition
Buildings and Improvements	617,000
Gross Amounts at Which Carried at Close of Period
Land	2,346,000
Buildings and Improvements	9,488,000
Total	11,834,000
Accumulated Depreciation	1,101,000
West Windsor [Member]
Costs Capitalized Subsequent to Acquisition
Land	53,000
Buildings and Improvements	23,617,000
Gross Amounts at Which Carried at Close of Period
Land	53,000
Buildings and Improvements	23,617,000
Total	23,670,000
Woodloch Forest 1400 [Member]
Costs Capitalized Subsequent to Acquisition
Land	1,570,000
Buildings and Improvements	14,045,000
Gross Amounts at Which Carried at Close of Period
Land	1,570,000
Buildings and Improvements	14,045,000
Total	15,615,000
Accumulated Depreciation	6,612,000
Corporate Segment [Member]
REAL ESTATE AND ACCUMULATED DEPRECIATION
Encumbrances	762,414,000
Initial Cost
Land	885,000
Buildings and Improvements	1,027,000
Costs Capitalized Subsequent to Acquisition
Land	(885,000)
Buildings and Improvements	16,336,000
Gross Amounts at Which Carried at Close of Period
Buildings and Improvements	17,363,000
Total	17,363,000
Accumulated Depreciation	$ 4,048,000