Earnings Per Share (Schedule of Earnings Per Basic And Diluted by Common Class) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income attributable to American Tower Corporation stockholders	$ 102,999	$ 207,593	$ 452,372	$ 644,523
Dividends on preferred stock	(26,781)	(7,700)	(63,382)	(12,075)
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION COMMON STOCKHOLDERS	$ 76,218	$ 199,893	$ 388,990	$ 632,448
Basic weighted average common shares outstanding (in shares)	423,375	396,243	417,280	395,758
Dilutive securities (in shares)	3,852	4,154	4,072	4,048
Diluted weighted average common shares outstanding (in shares)	427,227	400,397	421,352	399,806
Basic net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.18	$ 0.50	$ 0.93	$ 1.60
Diluted net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.18	$ 0.50	$ 0.92	$ 1.58