LONG-TERM OBLIGATIONS - Credit Facilities and Term Loans (Details) - American Tower Corporation $ in Millions	6 Months Ended
Jun. 30, 2026 USD ($) renewalPeriod
Revolving Credit Facility
Line of Credit Facility [Line Items]
Number of optional renewal periods \| renewalPeriod	2
2021 Multicurrency Credit Facility \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Outstanding principal balance	$ 1,085.0
Undrawn letters of credit	$ 18.7
Current margin over LIBOR or EURIBOR	0.875%
Current commitment fee, percentage	0.10%
2021 Credit Facility \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Outstanding principal balance	$ 695.0
Undrawn letters of credit	$ 20.7
Current margin over LIBOR or EURIBOR	0.875%
Current commitment fee, percentage	0.10%
2021 Term Loan \| Unsecured debt
Line of Credit Facility [Line Items]
Outstanding principal balance	$ 1,000.0
Current margin over LIBOR or EURIBOR	0.875%

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