Earnings Per Common 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, 2013	Mar. 31, 2012
NET INCOME PER COMMON SHARE AMOUNTS:
Income from continuing operations attributable to American Tower Corporation	$ 171,407	$ 221,306
Basic weighted average common shares outstanding	395,239	393,885
Dilutive securities	4,420	4,568
Diluted weighted average common shares outstanding	399,659	398,453
Basic income attributable to American Tower Corporation per common share	$ 0.43	$ 0.56
Diluted income attributable to American Tower Corporation per common share	$ 0.43	$ 0.56