Earnings Per Share (Schedule of Earnings Per Basic And Diluted by Common Class) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Net income attributable to American Tower Corporation stockholders	$ 193,317	$ 202,499
Dividends on preferred stock	(9,819)	0
NET INCOME ATTRIBUTABLE TO AMERICAN TOWER CORPORATION COMMON STOCKHOLDERS	$ 183,498	$ 202,499
Basic weighted average common shares outstanding (in shares)	405,111	395,146
Dilutive securities (in shares)	4,288	3,974
Diluted weighted average common shares outstanding (in shares)	409,399	399,120
Basic net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.45	$ 0.51
Diluted net income attributable to American Tower Corporation common stockholders per common share (in dollars per share)	$ 0.45	$ 0.51