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LONG-TERM OBLIGATIONS - Offerings of Senior Notes (Details) € in Millions, $ in Millions					9 Months Ended
	Sep. 16, 2025 USD ($)	May 30, 2025 USD ($)	May 30, 2025 EUR (€)	Mar. 14, 2025 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	May 30, 2025 EUR (€)	Dec. 31, 2024
Debt Instrument [Line Items]
Proceeds from issuance of senior long-term debt					$ 2,153.3	$ 2,374.1
Redemption price percentage					101.00%
Maximum adjusted EBITDA					3.5
Senior notes
Debt Instrument [Line Items]
Redemption price percentage					100.00%
American Tower Corporation \| Senior notes \| 4.900% senior notes
Debt Instrument [Line Items]
Debt interest rate (as a percent)	4.90%				4.90%
Aggregate principal amount	$ 850.0
American Tower Corporation \| Senior notes \| 5.350% senior notes
Debt Instrument [Line Items]
Debt interest rate (as a percent)	5.35%				5.35%
Aggregate principal amount	$ 725.0
American Tower Corporation \| Senior notes \| Initial 4.900% Senior Notes Due 2030 And Initial 5.350% Senior Notes Due 2035
Debt Instrument [Line Items]
Proceeds from issuance of senior long-term debt				$ 988.9
American Tower Corporation \| Senior notes \| Initial 4.900% senior notes
Debt Instrument [Line Items]
Debt interest rate (as a percent)				4.90%
Aggregate principal amount				$ 650.0
American Tower Corporation \| Senior notes \| Initial 5.350% senior notes
Debt Instrument [Line Items]
Debt interest rate (as a percent)				5.35%
Aggregate principal amount				$ 350.0
American Tower Corporation \| Senior notes \| Reopened 4.900% Senior Notes Due 2030 And Reopened 5.350% Senior Notes Due 2035
Debt Instrument [Line Items]
Proceeds from issuance of senior long-term debt	$ 587.8
American Tower Corporation \| Senior notes \| Reopened 4.900% senior notes
Debt Instrument [Line Items]
Debt interest rate (as a percent)	4.90%
Aggregate principal amount	$ 200.0
American Tower Corporation \| Senior notes \| Reopened 5.350% senior notes
Debt Instrument [Line Items]
Debt interest rate (as a percent)	5.35%
Aggregate principal amount	$ 375.0
American Tower Corporation \| Senior notes \| 2.400% senior notes
Debt Instrument [Line Items]
Debt interest rate (as a percent)				2.40%				2.40%
American Tower Corporation \| Senior notes \| 3.625% senior notes
Debt Instrument [Line Items]
Debt interest rate (as a percent)		3.625%			3.625%		3.625%
Aggregate principal amount		$ 567.4					€ 500.0
Proceeds from issuance of senior long-term debt		$ 563.7	€ 496.8