Selected Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Selected Quarterly Financial Data
Operating revenues	$ 768,374		$ 713,335		$ 697,734		$ 696,517		$ 653,199		$ 630,403		$ 597,235		$ 562,695		$ 2,875,960		$ 2,443,532		$ 1,985,335
Cost of operations	194,206	[1]	184,904	[1]	172,384	[1]	170,985	[1]	165,618	[1]	168,933	[1]	151,077	[1]	135,328	[1]	722,479	[1]	620,956	[1]
Operating income	279,235		295,552		270,486		274,446		247,738		228,305		225,789		218,300		1,119,719		920,132		784,378
Net income	118,153		231,825		33,689		210,358		196,434		(19,726)		113,171		91,961		594,025		381,840		373,606
Net income attributable to American Tower Corporation	$ 135,679		$ 232,089		$ 48,209		$ 221,306		$ 205,110		$ (15,701)		$ 115,211		$ 91,842		$ 637,283		$ 396,462		$ 372,936
Basic net income per common share (in dollars per share)	$ 0.34		$ 0.59		$ 0.12		$ 0.56		$ 0.52		$ (0.04)		$ 0.29		$ 0.23		$ 1.61		$ 1.00		$ 0.93
Diluted net income per common share (in dollars per share)	$ 0.34		$ 0.58		$ 0.12		$ 0.56		$ 0.52		$ (0.04)		$ 0.29		$ 0.23		$ 1.60		$ 0.99		$ 0.92

[1] Represents operating expenses, exclusive of depreciation, amortization and accretion, selling, general, administrative and development expense, and other operating expense.