LONG-TERM OBLIGATIONS - SCHEDULE OF LONG-TERM OBLIGATIONS (Details) € in Millions, $ in Millions	3 Months Ended	4 Months Ended
	Mar. 31, 2020 USD ($)	Apr. 29, 2020 EUR (€)	Apr. 29, 2020 USD ($)	Jan. 15, 2020	Jan. 10, 2020	Dec. 31, 2019 USD ($)	Feb. 14, 2019
Debt Instrument [Line Items]
Finance lease obligations	$ 25.6					$ 30.7
Total	24,577.4					24,055.4
Less current portion of long-term obligations	(2,640.0)					(2,928.2)
Long-term obligations	21,937.4					21,127.2
American Tower Corporation
Debt Instrument [Line Items]
Long-term debt	21,779.2					20,942.5
American Tower subsidiary
Debt Instrument [Line Items]
Long-term debt	$ 2,772.6					3,082.2
2019 364-Day Term Loan | Unsecured debt | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt term	364 days						364 days
Long-term debt	$ 0.0					999.9
2020 Term Loan | Unsecured debt | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt	749.9					0.0
2019 Multicurrency Credit Facility | Credit Facility | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt	965.4					700.0
2019 Term Loan | Unsecured debt | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt	995.4					995.2
2019 Credit Facility | Credit Facility | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt	$ 1,415.0					1,600.0
2.800% senior notes | Senior notes
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	2.80%
2.800% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	2.80%
Long-term debt	$ 749.7					749.4
3.300% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.30%
Long-term debt	$ 748.8					748.5
3.450% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.45%
Long-term debt	$ 648.0					647.7
5.900% Senior Notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	5.90%			5.90%
Long-term debt	$ 0.0					498.9
2.250% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	2.25%
Long-term debt	$ 605.7					592.1
4.70% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	4.70%
Long-term debt	$ 698.4					698.2
3.50% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.50%
Long-term debt	$ 994.7					994.3
3.000% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.00%
Long-term debt	$ 723.9					704.9
5.00% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	5.00%
Long-term debt	$ 1,001.6					1,001.7
3.375% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.375%
Long-term debt	$ 644.7					644.4
2.950% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	2.95%
Long-term debt	$ 641.7					641.3
2.400% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	2.40%				2.40%
Long-term debt	$ 744.2					0.0
1.375% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	1.375%
Long-term debt	$ 544.5					553.0
4.000% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	4.00%
Long-term debt	$ 743.5					743.2
4.400% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	4.40%
Long-term debt	$ 496.7					496.6
1.950% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	1.95%
Long-term debt	$ 545.8					554.4
3.375% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.375%
Long-term debt	$ 988.3					987.9
3.125% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.125%
Long-term debt	$ 397.7					397.6
2.750% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	2.75%
Long-term debt	$ 743.7					743.5
3.55% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.55%
Long-term debt	$ 744.3					744.1
3.600% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.60%
Long-term debt	$ 692.8					692.6
3.950% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.95%
Long-term debt	$ 589.8					589.6
3.800% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.80%
Long-term debt	$ 1,632.1					1,631.7
2.900% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	2.90%				2.90%
Long-term debt	$ 741.1					0.0
3.700% senior notes | Senior notes | American Tower Corporation
Debt Instrument [Line Items]
Long-term debt, stated interest rate (as a percent)	3.70%
Long-term debt	$ 591.8					591.8
Series 2013-2A securities | Secured debt | American Tower subsidiary
Debt Instrument [Line Items]
Long-term debt	1,295.4					1,295.0
Series 2018-1A securities | Secured debt | American Tower subsidiary
Debt Instrument [Line Items]
Long-term debt	494.0					493.8
Series 2015-1 notes | Secured debt | American Tower subsidiary
Debt Instrument [Line Items]
Long-term debt	349.9					349.6
Series 2015-2 notes | Secured debt | American Tower subsidiary
Debt Instrument [Line Items]
Long-term debt	521.6					521.4
Other subsidiary debt | Unsecured debt | American Tower subsidiary
Debt Instrument [Line Items]
Long-term debt	$ 111.7					$ 422.4
Debt repayment period	3 years
Other subsidiary debt | Unsecured debt | American Tower subsidiary | Subsequent Event
Debt Instrument [Line Items]
Repayment of loans		€ 24.5	$ 26.8