Ground Leases - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified

12 Months Ended

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Schedule of Operating Leases [Line Items]

Description of Lessor Leasing Arrangements, Operating Leases

The majority of the lease terms require twelve equal payments per year plus additional rents calculated as a percentage of gross revenues. The Colony Cove Property lease requires escalated payments every three months based on the increase in the purchase option, see further detail below.

Operating Lease, rent revenue

$ 3.3

$ 2.5

$ 1.9

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.

Operating lease annual payment, if the Company does not exercise option as planned

$ 1.4

Operating lease payments period, if the Company does not exercise option as planned

95 years

Minimum

Schedule of Operating Leases [Line Items]

Ground leases, expiration period year

2013

Maximum

Schedule of Operating Leases [Line Items]

Ground leases, expiration period year

2054