Subsequent Events (Details) (USD $)	0 Months Ended
Jan. 31, 2013	Jan. 08, 2013
Mexico Axtel Acquisition [Member]
Aggregate purchase price	$ 248,500,000
Number Of Sites Acquired	883
Three Point Five Zero Notes [Member]
Proceeds from Issuance of Debt		983,400,000
Debt Amount Of Principal Redemption Percentage		100.00%
Repurchase Price As Percentage Of Principal		101.00%
Repayment of indebtedness under credit facility	718,400,000	265,000,000
Debt Instrument Interest Rate		3.50%
Debt Issuance Percentage Less Discount		99.185%
Debt Instrument, Face Amount	$ 1,000,000,000	$ 1,000,000,000

Debt Amount Of Principal Redemption Percentage

No definition available.

Name:	amt_DebtAmountOfPrincipalRedemptionPercentage
Namespace Prefix:	amt_
Data Type:	num:percentItemType
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Period Type:	instant

- Definition

The percentage of debt that was originally recognized less the discount at the issuance of the instrument .

+ References

No definition available.

+ Details

Name:	amt_DebtIssuancePercentageLessDiscount
Namespace Prefix:	amt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Communications Sites Acquired

+ References

No definition available.

+ Details

Name:	amt_NumberOfSitesAcquired
Namespace Prefix:	amt_
Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	instant

- Definition

Repayment of indebtedness under credit facility

+ References

No definition available.

+ Details

Name:	amt_RepaymentOfIndebtednessUnderRevolvingCreditFacility
Namespace Prefix:	amt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Repurchase price as percentage of principal

+ References

No definition available.

+ Details

Name:	amt_RepurchasePriceAsPercentageOfPrincipal
Namespace Prefix:	amt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Interest rate stated in the contractual debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

No definition available.

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration