LONG-TERM OBLIGATIONS - SCHEDULE OF LINES OF CREDIT (Details) - American Tower Corporation $ in Millions		9 Months Ended
	Feb. 13, 2020	Sep. 30, 2020 USD ($) renewal_period
Credit Facility
Line of Credit Facility [Line Items]
Optional renewal periods | renewal_period		2
2019 Multicurrency Credit Facility | Credit Facility
Line of Credit Facility [Line Items]
Outstanding Principal Balance		$ 0.0
Undrawn letters of credit		$ 3.8
Current commitment fee (as a percent)		0.11%
2019 Multicurrency Credit Facility | Credit Facility | Current margin over LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)		1.125%
2019 Credit Facility | Credit Facility
Line of Credit Facility [Line Items]
Outstanding Principal Balance		$ 390.0
Undrawn letters of credit		$ 0.8
Current commitment fee (as a percent)		0.11%
2019 Credit Facility | Credit Facility | Current margin over LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)		1.125%
2019 Term Loan | Unsecured debt
Line of Credit Facility [Line Items]
Outstanding Principal Balance		$ 1,000.0
2019 Term Loan | Unsecured debt | Current margin over LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)		1.125%
2020 Term Loan | Unsecured debt
Line of Credit Facility [Line Items]
Outstanding Principal Balance		$ 750.0
2020 Term Loan | Unsecured debt | Current margin over LIBOR
Line of Credit Facility [Line Items]
Current margin over LIBOR (as a percent)	0.65%	0.65%