Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013 Tower	Mar. 31, 2012
Business Acquisition Information [Line Items]
Number of towers acquired	41
Acquisition of capital expenditures	$ 209,542,000	$ 51,148,000
Ground lease extensions	1,700,000	1,500,000
Estimated contingent consideration fair value	600,000	1,400,000
Potential obligation recorded in accrued expenses	8,900,000
Brazil acquisition [Member]
Business Acquisition Information [Line Items]
Acquisition of capital expenditures	$ 175,900,000