Organization and significant policies (Details)	Dec. 31, 2012
Percentage of common stock by subsidiaries of ARL	83.80%
Percentage of common stock of Income Opportunity Realty Investors, Inc. By TCI	81.10%
Number of interests in a total property portfolio of income producing properties	60
Number of commercial buildings	13
Number of office buildings	10
Number of industrial warehouse	1
Number of retails centers	3
Number of apartment communities	47
Apartment communities units total	8,533
Area of acres of developed and undeveloped land	4,133
Buildings and improvements minimum useful life	10
Buildings and improvements maximum useful life	40
Furniture, fixtures and equipment minimum useful life	5
Furniture, fixtures and equipment maximum useful life	10
Historical accounting value of IOT's assets in millions	112
Historical accounting value of IOT's liabilities in millions	43
Net difference between the purchase price and historical accounting basis of the assets and liabilities in millions	26.9