Acquisitions - Additional Information (Detail) In Millions, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended		1 Months Ended	12 Months Ended
	Dec. 31, 2012 USD ($) Tower	Dec. 31, 2011 USD ($) Tower	Dec. 31, 2010 USD ($) Tower	Apr. 02, 2012 Mobilitie [Member] USD ($) Tower	Dec. 31, 2012 Mobilitie [Member] USD ($)	Oct. 31, 2012 TowerCo [Member] USD ($) Tower State	Dec. 31, 2012 TowerCo [Member] USD ($)	Apr. 02, 2012 TowerCo [Member] USD ($)	Dec. 20, 2012 Brazil Acquisition [Member] BRL Tower	Dec. 31, 2012 Brazil Acquisition [Member] Tower	Dec. 31, 2012 Other Acquisition [Member] Tower
Business Acquisition Information [Line Items]
Owned towers	17,491			2,281		3,256
Additional towers in development				36
Aggregate purchase price				$ 1,100.0					175.9
Total consideration paid in cash				850.0		1,200.0
Newly issued shares				5,250,000		4,588,840
Transaction costs associated with acquisition				13.6				17.0
Revenues from acquisition					83.3		42.4
Net loss from acquisition					23.6		18.8
Number of states, tower sites acquired						47
Number of freestanding wireless towers acquired	6,630	1,085	712						800	800	1,093
Long-term lease extensions	9.7	9.8	9.0
Contingent consideration, expense, net	0.8
Contingent consideration, income, net		0.7
Potential obligation recorded in accrued expenses	$ 9.8	$ 5.5