Basis of presentation (Policies)	6 Months Ended
Basis of presentation (Policies)	Jun. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	Basis of presentation We have prepared the accompanying interim consolidated financial statements in accordance with U.S. generally accepted accounting principles (“GAAP”) and in conformity with the rules and regulations of the Securities and Exchange Commission (“SEC”). In our opinion, the interim consolidated financial statements presented herein reflect all adjustments that are necessary to fairly present the interim consolidated financial statements. The results of operations for the interim period are not necessarily indicative of the results that may be expected for the year ending December 31, 2014. These consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in our annual report on Form 10-K for the year ended December 31, 2013. The accompanying consolidated financial statements include the accounts of Alexandria Real Estate Equities, Inc. and its consolidated subsidiaries. All significant intercompany balances and transactions have been eliminated. We hold interests, together with certain third parties, in companies that we consolidate in our financial statements. We consolidate the companies because we exercise significant control over major decisions by these entities, such as investment activity and changes in financing.
Reclassifications	Reclassifications Certain prior period amounts have been reclassified to conform to the current period presentation for discontinued operations.
Use of estimates	Use of estimates The preparation of consolidated financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities, and equity; the disclosure of contingent assets and liabilities as of the date of the consolidated financial statements; and the amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates.
Investments in real estate, net, and discontinued operations	Investments in real estate, net, and discontinued operations We recognize real estate acquired (including the intangible value of above or below market leases, acquired in-place leases, client tenant relationships, and other intangible assets or liabilities), liabilities assumed, and any noncontrolling interest in an acquired entity at their fair value as of the acquisition date. If there is a bargain fixed-rate renewal option for the period beyond the non-cancelable lease term, we evaluate factors such as the business conditions in the industry in which the lessee operates, the economic conditions in the area in which the property is located, and the ability of the lessee to sublease the property during the renewal term, in order to determine the likelihood that the lessee will renew. When we determine there is reasonable assurance that such bargain purchase option will be exercised, we consider its impact in determining the intangible value of such lease and its related amortization period. The value of tangible assets acquired is based upon our estimation of value on an “as if vacant” basis. The value of acquired in-place leases includes the estimated costs during the hypothetical lease-up period and other costs that would have been incurred in the execution of similar leases, considering market conditions at the acquisition date of the acquired in-place lease. We assess the fair value of tangible and intangible assets based on numerous factors, including estimated cash flow projections that utilize appropriate discount and capitalization rates and available market information. Estimates of future cash flows are based on a number of factors, including the historical operating results, known trends, and market/economic conditions that may affect the property. We also recognize the fair values of assets acquired, the liabilities assumed, and any noncontrolling interest in acquisitions of less than a 100% interest when the acquisition constitutes a change in control of the acquired entity. Costs related to the acquisition of businesses, including real estate acquired with in-place leases, are expensed as incurred. The values allocated to buildings and building improvements, land improvements, tenant improvements, and equipment are depreciated on a straight-line basis using the shorter of the term of the respective ground lease and up to 40 years for buildings and building improvements, an estimated life of 20 years for land improvements, the respective lease term for tenant improvements, and the estimated useful life for equipment. The values of acquired above and below market leases are amortized over the lives of the related leases and recognized as either an increase (for below market leases) or a decrease (for above market leases) to rental income. The values of acquired in-place leases are classified in other assets in the accompanying consolidated balance sheets, and amortized over the remaining terms of the related leases. We are required to capitalize project costs, including predevelopment costs, interest, property taxes, insurance, and other costs directly related and essential to the acquisition, development, redevelopment, predevelopment, or construction of a project. Capitalization of development, redevelopment, predevelopment, and construction costs is required while activities are ongoing to prepare an asset for its intended use. Fluctuations in our development, redevelopment, predevelopment, and construction activities could result in significant changes to total expenses and net income. Costs incurred after a project is substantially complete and ready for its intended use are expensed as incurred. Should development, redevelopment, predevelopment, or construction activities cease, interest, property taxes, insurance, and certain other costs would no longer be eligible for capitalization and would be expensed as incurred. Expenditures for repairs and maintenance are expensed as incurred. A property is classified as “held for sale” when all of the following criteria for a plan of sale have been met: (i) management, having the authority to approve the action, commits to a plan to sell the property; (ii) the property is available for immediate sale in its present condition, subject only to terms that are usual and customary; (iii) an active program to locate a buyer and other actions required to complete the plan to sell have been initiated; (iv) the sale of the property is probable and is expected to be completed within one year; (v) the property is being actively marketed for sale at a price that is reasonable in relation to its current fair value; and (vi) actions necessary to complete the plan of sale indicate that it is unlikely that significant changes to the plan will be made or that the plan will be withdrawn. When all of these criteria have been met, the property is classified as “held for sale,” and if (i) the operations and cash flows of the property have been or will be eliminated from the ongoing operations, and (ii) we will not have any significant continuing involvement in the operations of the property after the sale, then its operations, including any interest expense directly attributable to it, are classified as discontinued operations in our consolidated statements of income, and amounts for all prior periods presented are reclassified from continuing operations to discontinued operations. Depreciation of assets ceases upon designation of a property as “held for sale.”
Impairment of long-lived assets	Impairment of long-lived assets Long-lived assets to be held and used, including our rental properties, land held for development, construction in progress, and intangibles, are individually evaluated for impairment when conditions exist that may indicate that the amount of a long-lived asset may not be recoverable. The amount of a long-lived asset to be held and used is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. Impairment indicators or triggering events for long-lived assets to be held and used, including our rental properties, land held for development, and construction in progress, are assessed by project and include significant fluctuations in estimated net operating income (“NOI”), occupancy changes, significant near-term lease expirations, current and historical operating and/or cash flow losses, construction costs, estimated completion dates, rental rates, and other market factors. We assess the expected undiscounted cash flows based upon numerous factors, including, but not limited to, construction costs, available market information, current and historical operating results, known trends, current market/economic conditions that may affect the property, and our assumptions about the use of the asset, including, if necessary, a probability-weighted approach if multiple outcomes are under consideration. Upon determination that an impairment has occurred, a write-down is recognized to reduce the carrying amount to its estimated fair value. If an impairment loss is not required to be recognized, the recognition of depreciation is adjusted prospectively, as necessary, to reduce the carrying amount of the real estate to its estimated disposition value over the remaining period that the real estate is expected to be held and used. We may adjust depreciation of properties that are expected to be disposed of or redeveloped prior to the end of their useful lives. We use the “held for sale” impairment model for our properties classified as “held for sale.” The “held for sale” impairment model is different from the held and used impairment model. Under the “held for sale” impairment model, an impairment loss is recognized if the amount of the long-lived asset classified as “held for sale” exceeds its fair value less cost to sell. Because of these two different models, it is possible for a long-lived asset previously classified as held and used to require the recognition of an impairment charge upon classification as “held for sale.”
Investments	Investments We hold equity investments in certain publicly traded companies and investments in certain privately held entities primarily involved in the life science industry. All of our investments in actively traded public companies are considered “available for sale” and are reflected in the accompanying consolidated balance sheets at fair value. Fair value has been determined based upon the closing price as of each balance sheet date, with unrealized gains and losses shown as a separate component of comprehensive income. The classification of each investment is determined at the time each investment is made, and such determination is reevaluated at each balance sheet date. The cost of each investment sold is determined by the specific identification method, with realized gains or losses classified in other income in the accompanying consolidated statements of income. Investments in privately held entities and limited partnerships are generally accounted for under the cost method when our interest in the entity is so minor that we have virtually no influence over the entity’s operating and financial policies. Certain investments in privately held entities and limited partnerships are accounted for under the equity method when our interest in the entity is not deemed so minor that we have virtually no influence over the entity’s operating and financial policies. Under the equity method of accounting, we recognize our investment initially at cost and adjust the amount of the investment to recognize our share of the earnings or losses of the investee subsequent to the date of our investment. Additionally, we limit our ownership percentage in the voting interest of each individual entity to less than 10%. As of June 30, 2014, and December 31, 2013, our ownership percentage in the voting interest of each individual entity was less than 10%. We monitor each of our investments throughout the year for new developments, including operating results, results of clinical trials, capital-raising events, and merger and acquisition activities. Individual investments are evaluated for impairment when changes in conditions may indicate an impairment exists. The factors that we consider in making these assessments include, but are not limited to, market prices, market conditions, available financing, prospects for favorable or unfavorable clinical trial results, new product initiatives, and new collaborative agreements. If there are no identified events or changes in circumstances that would have an adverse effect on our cost method investments, we do not estimate the investment’s fair value. For all of our investments, if a decline in the fair value of an investment below the carrying value is determined to be other than temporary, such investment is written down to its estimated fair value with a charge to current earnings.
Income Taxes	Income taxes We are organized and qualify as a REIT pursuant to the Internal Revenue Code of 1986, as amended (the “Code”). Under the Code, a REIT that distributes 100% of its REIT taxable income as a dividend to its shareholders each year and that meets certain other conditions is not subject to federal income taxes, but could be subject to certain state and local taxes. We have distributed 100% or more of our taxable income. Therefore, no provision for federal income taxes is required. We file tax returns, including returns for our subsidiaries, with federal, state, and local jurisdictions, including jurisdictions located in the United States (“U.S.”), Canada, India, China, and other international locations. Our tax returns are subject to examination in various jurisdictions for the calendar years 2009 through 2013.
Recognition of rental income and tenant recoveries	Recognition of rental income and tenant recoveries Rental income from leases is recognized on a straight-line basis over the respective lease terms. We classify amounts currently recognized as income, and expected to be received in later years, as an asset in deferred rent in the accompanying consolidated balance sheets. Amounts received currently, but recognized as income in future years, are classified in accounts payable, accrued expenses, and tenant security deposits in the accompanying consolidated balance sheets. We commence recognition of rental income at the date the property is ready for its intended use and the client tenant takes possession of or controls the physical use of the property. Tenant recoveries related to reimbursement of real estate taxes, insurance, utilities, repairs and maintenance, and other operating expenses are recognized as revenue in the period during which the applicable expenses are incurred. Tenant receivables consist primarily of amounts due for contractual lease payments, reimbursements of common area maintenance expenses, property taxes, and other expenses recoverable from client tenants. Tenant receivables are expected to be collected within one year. We may maintain an allowance for estimated losses that may result from the inability of our client tenants to make payments required under the terms of the lease and for tenant recoveries due. If a client tenant fails to make contractual payments beyond any allowance, we may recognize additional bad debt expense in future periods equal to the amount of uncollectible rent and deferred rent receivables arising from the straight-lining of rent. As of June 30, 2014, and December 31, 2013, we had no allowance for estimated losses.
Monitoring client tenant credit quality	Monitoring client tenant credit quality During the term of each lease, we monitor the credit quality of our client tenants by (i) reviewing the credit rating of tenants that are rated by a nationally recognized credit rating agency, (ii) reviewing financial statements of the client tenants that are publicly available or that are required to be delivered to us pursuant to the applicable lease, (iii) monitoring news reports regarding our client tenants and their respective businesses, and (iv) monitoring the timeliness of lease payments. We have a team of employees who, among them, have graduate and undergraduate degrees in biology, chemistry, and industrial biotechnology and experience in the life science industry, as well as in finance. This research team is responsible for assessing and monitoring the credit quality of our client tenants and any material changes in credit quality.
Interest income	Interest income Interest income was $911 thousand and $990 thousand during the three months ended June 30, 2014 and 2013, respectively. Interest income was $1.8 million and $2.3 million during the six months ended June 30, 2014 and 2013, respectively. Interest income is included in other income in the accompanying consolidated statements of income.
Impact of recently issued accounting standards	Impact of recently issued accounting standards In April 2014, the Financial Accounting Standards Board (“FASB”) issued an Accounting Standards Update (“ASU”) on the reporting of discontinued operations, which raises the threshold for disposals to qualify as discontinued operations. Under this ASU, a discontinued operation is (i) a component of an entity or group of components that has been disposed of by sale, that has been disposed of other than by sale, or that is classified as “held for sale” and represents a strategic shift that has had or will have a major effect on an entity’s operations and financial results or (ii) an acquired business or nonprofit activity that is classified as “held for sale” on the date of the acquisition. A strategic shift that has or will have a major effect on an entity’s operations and financial results could include the disposal of (i) a major line of business, (ii) a major geographic area, (iii) a major equity method investment, or (iv) other major parts of an entity. Under current GAAP, an entity is prohibited from reporting a discontinued operation if it has certain continuing cash flows or involvement with the component after the disposal. This ASU eliminates these criteria and is effective for public companies during the interim and annual periods, beginning after December 15, 2014. We are required to adopt this ASU no later than January 1, 2015 and may early adopt this ASU during interim periods, as applicable. We expect the adoption of this ASU to result in fewer real estate sales qualifying for classification as discontinued operations in our consolidated financial statements. In May 2014, the FASB issued an ASU that replaces substantially all industry-specific revenue recognition requirements and converges areas under this topic with International Financial Reporting Standards. The ASU implements a five-step process for customer contract revenue recognition that focuses on transfer of control, as opposed to transfer of risk and rewards. The ASU also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenues and cash flows from contracts with customers. Other major provisions in this ASU include capitalizing and amortizing certain contract costs, ensuring the time value of money is considered in the applicable transaction price, and allowing estimates of variable consideration to be recognized before contingencies are resolved in certain circumstances. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. The ASU is effective for reporting periods beginning after December 15, 2016, and early adoption is prohibited. The ASU does not apply to lease contracts accounted for under current GAAP. We are currently evaluating the impact of the adoption of this ASU will have on our financial position and results of operations.