Accounting for the Impairment of Long-Lived Assets and Fee Development Contracts	9 Months Ended
Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Asset Impairment Charges [Text Block]	Accounting for the Impairment of Long-Lived Assets and Fee Development Contracts Impairment Charges - Real Estate Assets The Company disposes of and anticipates the potential disposition of certain properties prior to the end of their remaining useful lives. During the three and nine months ended September 30, 2017 the Company recognized $9.7 million in impairment charges which related to the Company's Houston reportable segment. There were no impairment charges recognized during the three or nine months ended September 30, 2016. The Company determined these impairments based on third party offer prices and quoted offer prices for comparable transactions which are Level 2 and Level 3 inputs, respectively, according to the fair value hierarchy established in ASC 820. These measurements have occurred as circumstances arise, and the resulting estimates of fair value are not necessarily reflective of measurements at the period’s end. The Company has applied reasonable additional estimates and judgments in evaluating each of its properties and land held for development and has determined that there were no additional valuation adjustments necessary at September 30, 2017. Should external or internal circumstances change requiring the need to shorten the holding periods or adjust the estimated future cash flows of the Company’s assets, the Company could be required to record impairment charges in the future. Fee Development Contracts From time to time, the Company enters into contracts to develop properties on a fee basis for joint ventures in which the Company holds an interest or for unrelated third parties. In these cases the Company typically agrees to be responsible for all aspects of the development of the project (and, in certain instances, related infrastructure) and to guarantee the timely lien-free completion of construction of the project and the payment, subject to certain exceptions, of cost overruns incurred in the development of the project. If the Company encounters construction delays or unexpected costs in the development of these projects or is otherwise unable to recover the costs it incurs, the resulting unrecovered costs and potential payments to customers could generate losses that would adversely affect the Company's cash flow and net income. On a quarterly basis, the Company applies reasonable estimates and judgments to assess whether or not it is necessary to accrue any estimated future losses with respect to such contracts. There were no such losses recognized during the three or nine months ended September 30, 2017 or 2016. Should external or internal circumstances change requiring the Company to adjust the estimated future cash flows from these development contracts or that suggest that such development contracts may result in a loss, the Company could be required to record losses in the future. Expensed Pursuit Costs The Company capitalizes pre-development costs incurred in pursuit of new development opportunities for which the Company currently believes future development is probable. Future development is dependent upon various factors, including zoning and regulatory approval, rental market conditions and construction costs. Initial pre-development costs incurred for pursuits for which future development is not yet considered probable are expensed as incurred. In addition, if the status of a future development by the Company is no longer probable, any capitalized pre-development costs are written off with a charge to expense. The Company expensed costs related to pursuit costs of $4.8 million and $5.0 million for the three and nine months ended September 30, 2017 and $772,000 and $882,000 for the three and nine months ended September 30, 2016. These costs are included in expensed pursuit costs on the accompanying Consolidated Statements of Comprehensive Income.

Accounting for the Impairment of Long-Lived Assets and Fee Development Contracts

Impairment Charges - Real Estate Assets

The Company disposes of and anticipates the potential disposition of certain properties prior to the end of their remaining useful lives. During the three and nine months ended September 30, 2017 the Company recognized $9.7 million in impairment charges which related to the Company's Houston reportable segment. There were no impairment charges recognized during the three or nine months ended September 30, 2016. The Company determined these impairments based on third party offer prices and quoted offer prices for comparable transactions which are Level 2 and Level 3 inputs, respectively, according to the fair value hierarchy established in ASC 820. These measurements have occurred as circumstances arise, and the resulting estimates of fair value are not necessarily reflective of measurements at the period’s end. The Company has applied reasonable additional estimates and judgments in evaluating each of its properties and land held for development and has determined that there were no additional valuation adjustments necessary at September 30, 2017. Should external or internal circumstances change requiring the need to shorten the holding periods or adjust the estimated future cash flows of the Company’s assets, the Company could be required to record impairment charges in the future.

Fee Development Contracts

From time to time, the Company enters into contracts to develop properties on a fee basis for joint ventures in which the Company holds an interest or for unrelated third parties. In these cases the Company typically agrees to be responsible for all aspects of the development of the project (and, in certain instances, related infrastructure) and to guarantee the timely lien-free completion of construction of the project and the payment, subject to certain exceptions, of cost overruns incurred in the development of the project. If the Company encounters construction delays or unexpected costs in the development of these projects or is otherwise unable to recover the costs it incurs, the resulting unrecovered costs and potential payments to customers could generate losses that would adversely affect the Company's cash flow and net income. On a quarterly basis, the Company applies reasonable estimates and judgments to assess whether or not it is necessary to accrue any estimated future losses with respect to such contracts. There were no such losses recognized during the three or nine months ended September 30, 2017 or 2016. Should external or internal circumstances change requiring the Company to adjust the estimated future cash flows from these development contracts or that suggest that such development contracts may result in a loss, the Company could be required to record losses in the future.

Expensed Pursuit Costs

The Company capitalizes pre-development costs incurred in pursuit of new development opportunities for which the Company currently believes future development is probable. Future development is dependent upon various factors, including zoning and regulatory approval, rental market conditions and construction costs. Initial pre-development costs incurred for pursuits for which future development is not yet considered probable are expensed as incurred. In addition, if the status of a future development by the Company is no longer probable, any capitalized pre-development costs are written off with a charge to expense. The Company expensed costs related to pursuit costs of $4.8 million and $5.0 million for the three and nine months ended September 30, 2017 and $772,000 and $882,000 for the three and nine months ended September 30, 2016. These costs are included in expensed pursuit costs on the accompanying Consolidated Statements of Comprehensive Income.