Description of Business, Basis of Presentation and Accounting Policies	3 Months Ended
Mar. 31, 2013
Description Of Business And Basis Of Presentation Disclosure [Abstract]
Description of Business, Basis of Presentation and Accounting Policies	1. Description of Business, Basis of Presentation and Accounting Policies American Tower Corporation is, through its various subsidiaries (collectively, “ATC” or the “Company”), an independent owner, operator and developer of wireless and broadcast communications real estate in the United States, Brazil, Chile, Colombia, Germany, Ghana, India, Mexico, Peru, South Africa and Uganda. The Company's primary business is the leasing of antenna space on multi-tenant communications sites to wireless service providers, radio and television broadcast companies, wireless data and data providers, government agencies and municipalities and tenants in a number of other industries. The Company also manages rooftop and tower sites for property owners, operates in-building and outdoor distributed antenna system (“DAS”) networks, holds property interests under third-party communications sites and provides network development services that primarily support its rental and management operations and the addition of new tenants and equipment on its sites. The Company began operating as a real estate investment trust for federal income tax purposes (“REIT”) effective January 1, 2012. ATC is a holding company that conducts its operations through its directly and indirectly owned subsidiaries and its joint ventures. ATC's principal domestic operating subsidiaries are American Towers LLC and SpectraSite Communications, LLC. ATC conducts its international operations through its subsidiary, American Tower International, Inc., which in turn conducts operations through its various international operating subsidiaries and joint ventures. The accompanying condensed consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). The financial information included herein is unaudited; however, the Company believes that all adjustments (consisting primarily of normal recurring adjustments) considered necessary for a fair presentation of the Company's financial position and results of operations for such periods have been included. These condensed consolidated financial statements and related notes should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2012. The Company believes that since January 1, 2012, it has been organized and has operated in a manner that enables it to qualify, and intends to continue to operate in a manner that will allow it to continue to qualify, as a REIT for federal income tax purposes. The Company holds and operates certain of its assets through one or more taxable REIT subsidiaries (“TRSs”). A TRS is a subsidiary of a REIT that is subject to applicable corporate income tax. The Company's use of TRSs enables it to continue to engage in certain businesses while complying with REIT qualification requirements and also allows the Company to retain income generated by these businesses for reinvestment without the requirement of distributing those earnings. The non-REIT qualified businesses that the Company holds through TRSs include its network development services segment. In addition, the Company has included most of its international operations and DAS networks business within its TRSs. The Company changed the election for substantially all of its Mexican operations, all of which was previously designated as a TRS, to be treated as a qualified REIT subsidiary as of March 1, 2013. Although the election did not have a material effect on the Company's deferred tax position, the Company recognized a one-time dividend from its Mexican operations, the income from which the Company may either offset with its net operating losses or distribute to its stockholders as part of its regular distributions. For all periods subsequent to March 1, 2013, the Company will be required to include the income from its Mexican operations as part of its REIT taxable income for the purpose of computing the Company's REIT distribution requirements. The Company is also considering changing the election of other previously designated TRSs, which hold certain of its other international operations, to be treated as qualified REIT subsidiaries or other disregarded entities (collectively, “QRSs”), and may reorganize and transfer certain assets or operations from its TRSs to other subsidiaries, including QRSs. As a REIT, the Company generally will not be subject to federal income taxes on its income and gains that the Company distributes to its stockholders, including the income derived from leasing towers. However, even as a REIT, the Company will remain obligated to pay income taxes on earnings from its TRS assets. In addition, the Company's international assets and operations continue to be subject to taxation in the foreign jurisdictions where those assets are held or those operations are conducted. Principles of Consolidation and Basis of Presentation—The accompanying condensed consolidated financial statements include the accounts of the Company and those entities in which it has a controlling interest. Investments in entities that the Company does not control are accounted for using the equity or cost method, depending upon the Company's ability to exercise significant influence over operating and financial policies. All intercompany accounts and transactions have been eliminated. Significant Accounting Policies and Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States (“GAAP”) requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results may differ from those estimates, and such differences could be material to the accompanying condensed consolidated financial statements. The significant estimates in the accompanying condensed consolidated financial statements include impairment of long-lived assets (including goodwill), asset retirement obligations, revenue recognition, rent expense, stock-based compensation, income taxes and accounting for business combinations. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued as additional evidence for certain estimates or to identify matters that require additional disclosure. Recently Adopted Accounting Standards— In February 2013, the Financial Accounting Standards Board (“FASB”) issued additional guidance on comprehensive income which adds new disclosure requirements for items reclassified out of accumulated other comprehensive income (“AOCI”) by component. This guidance enhances the transparency of changes in other comprehensive income (“OCI”) and items transferred out of AOCI in the financial statements and it does not amend any existing requirements for reporting net income or OCI in the financial statements. Since the guidance relates only to presentation and disclosure of information, the adoption did not have a material effect on the Company's condensed consolidated financial condition or results of operations. In February 2013, the FASB issued guidance that clarifies the scope of transactions subject to disclosures about offsetting assets and liabilities. The guidance requires an entity to disclose information about offsetting and related arrangements to enable users of its financial statements to understand the effect of those arrangements on its financial position. This guidance is effective for annual and interim reporting periods beginning on or after January 1, 2013 on a retrospective basis. The adoption of this guidance did not have a material impact on the Company's disclosures in the condensed consolidated financial statements.

Description of Business, Basis of Presentation and Accounting Policies

3 Months Ended

Mar. 31, 2013

Description Of Business And Basis Of Presentation Disclosure [Abstract]

Description of Business, Basis of Presentation and Accounting Policies

1. Description of Business, Basis of Presentation and Accounting Policies

American Tower Corporation is, through its various subsidiaries (collectively, “ATC” or the “Company”), an independent owner, operator and developer of wireless and broadcast communications real estate in the United States, Brazil, Chile, Colombia, Germany, Ghana, India, Mexico, Peru, South Africa and Uganda. The Company's primary business is the leasing of antenna space on multi-tenant communications sites to wireless service providers, radio and television broadcast companies, wireless data and data providers, government agencies and municipalities and tenants in a number of other industries. The Company also manages rooftop and tower sites for property owners, operates in-building and outdoor distributed antenna system (“DAS”) networks, holds property interests under third-party communications sites and provides network development services that primarily support its rental and management operations and the addition of new tenants and equipment on its sites. The Company began operating as a real estate investment trust for federal income tax purposes (“REIT”) effective January 1, 2012.

ATC is a holding company that conducts its operations through its directly and indirectly owned subsidiaries and its joint ventures. ATC's principal domestic operating subsidiaries are American Towers LLC and SpectraSite Communications, LLC. ATC conducts its international operations through its subsidiary, American Tower International, Inc., which in turn conducts operations through its various international operating subsidiaries and joint ventures.

The accompanying condensed consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). The financial information included herein is unaudited; however, the Company believes that all adjustments (consisting primarily of normal recurring adjustments) considered necessary for a fair presentation of the Company's financial position and results of operations for such periods have been included. These condensed consolidated financial statements and related notes should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2012.

The Company believes that since January 1, 2012, it has been organized and has operated in a manner that enables it to qualify, and intends to continue to operate in a manner that will allow it to continue to qualify, as a REIT for federal income tax purposes.

The Company holds and operates certain of its assets through one or more taxable REIT subsidiaries (“TRSs”). A TRS is a subsidiary of a REIT that is subject to applicable corporate income tax. The Company's use of TRSs enables it to continue to engage in certain businesses while complying with REIT qualification requirements and also allows the Company to retain income generated by these businesses for reinvestment without the requirement of distributing those earnings. The non-REIT qualified businesses that the Company holds through TRSs include its network development services segment. In addition, the Company has included most of its international operations and DAS networks business within its TRSs. The Company changed the election for substantially all of its Mexican operations, all of which was previously designated as a TRS, to be treated as a qualified REIT subsidiary as of March 1, 2013. Although the election did not have a material effect on the Company's deferred tax position, the Company recognized a one-time dividend from its Mexican operations, the income from which the Company may either offset with its net operating losses or distribute to its stockholders as part of its regular distributions. For all periods subsequent to March 1, 2013, the Company will be required to include the income from its Mexican operations as part of its REIT taxable income for the purpose of computing the Company's REIT distribution requirements.

The Company is also considering changing the election of other previously designated TRSs, which hold certain of its other international operations, to be treated as qualified REIT subsidiaries or other disregarded entities (collectively, “QRSs”), and may reorganize and transfer certain assets or operations from its TRSs to other subsidiaries, including QRSs.

As a REIT, the Company generally will not be subject to federal income taxes on its income and gains that the Company distributes to its stockholders, including the income derived from leasing towers. However, even as a REIT, the Company will remain obligated to pay income taxes on earnings from its TRS assets. In addition, the Company's international assets and operations continue to be subject to taxation in the foreign jurisdictions where those assets are held or those operations are conducted.

Principles of Consolidation and Basis of Presentation—The accompanying condensed consolidated financial statements include the accounts of the Company and those entities in which it has a controlling interest. Investments in entities that the Company does not control are accounted for using the equity or cost method, depending upon the Company's ability to exercise significant influence over operating and financial policies. All intercompany accounts and transactions have been eliminated.

Significant Accounting Policies and Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States (“GAAP”) requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results may differ from those estimates, and such differences could be material to the accompanying condensed consolidated financial statements. The significant estimates in the accompanying condensed consolidated financial statements include impairment of long-lived assets (including goodwill), asset retirement obligations, revenue recognition, rent expense, stock-based compensation, income taxes and accounting for business combinations. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued as additional evidence for certain estimates or to identify matters that require additional disclosure.

Recently Adopted Accounting Standards— In February 2013, the Financial Accounting Standards Board (“FASB”) issued additional guidance on comprehensive income which adds new disclosure requirements for items reclassified out of accumulated other comprehensive income (“AOCI”) by component. This guidance enhances the transparency of changes in other comprehensive income (“OCI”) and items transferred out of AOCI in the financial statements and it does not amend any existing requirements for reporting net income or OCI in the financial statements. Since the guidance relates only to presentation and disclosure of information, the adoption did not have a material effect on the Company's condensed consolidated financial condition or results of operations.

In February 2013, the FASB issued guidance that clarifies the scope of transactions subject to disclosures about offsetting assets and liabilities. The guidance requires an entity to disclose information about offsetting and related arrangements to enable users of its financial statements to understand the effect of those arrangements on its financial position. This guidance is effective for annual and interim reporting periods beginning on or after January 1, 2013 on a retrospective basis. The adoption of this guidance did not have a material impact on the Company's disclosures in the condensed consolidated financial statements.

- Definition

The entire disclosure for the organization, consolidation and basis of presentation of financial statements disclosure, and significant accounting policies of the reporting entity. May be provided in more than one note to the financial statements, as long as users are provided with an understanding of (1) the significant judgments and assumptions made by an enterprise in determining whether it must consolidate a VIE and/or disclose information about its involvement with a VIE, (2) the nature of restrictions on a consolidated VIE's assets reported by an enterprise in its statement of financial position, including the carrying amounts of such assets, (3) the nature of, and changes in, the risks associated with an enterprise's involvement with the VIE, and (4) how an enterprise's involvement with the VIE affects the enterprise's financial position, financial performance, and cash flows. Describes procedure if disclosures are provided in more than one note to the financial statements.

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