Lease Agreements - Additional Information (Detail)	12 Months Ended
Dec. 31, 2012 integer
Schedule of Operating Leases [Line Items]
Operating Lease terms	The leases entered into between the customer and the Company for the rental of a site are generally month-to-month or for a period of one to ten years, renewable upon the consent of the parties or, in some instances, as provided by statute.
Number of properties where non-cancelable long-term leases are in effect	18
Minimum
Schedule of Operating Leases [Line Items]
Operating Lease, expiration period year	1 year
Maximum
Schedule of Operating Leases [Line Items]
Operating Lease, expiration period year	10 years

Lease Agreements - Additional Information (Detail)

12 Months Ended

Dec. 31, 2012

integer

Schedule of Operating Leases [Line Items]

The leases entered into between the customer and the Company for the rental of a site are generally month-to-month or for a period of one to ten years, renewable upon the consent of the parties or, in some instances, as provided by statute.

Number of properties where non-cancelable long-term leases are in effect

Minimum

Schedule of Operating Leases [Line Items]

Operating Lease, expiration period year

1 year

Maximum

Schedule of Operating Leases [Line Items]

Operating Lease, expiration period year

10 years