Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Summary Of Significant Accounting Policies [Line Items]
Useful life of property	40 years
Depreciation expense from operation	$ 10.2	$ 8.5
Real estate cost capitalized excluding interest cost	2.2	1.7
Real estate interest cost capitalized incurred	1.6	1.0
In Place Leases [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of lease cost	0.6	0.6
Tenant Relationship [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of lease cost	$ 0.3	$ 0.4
Minimum [Member] | Land, Buildings and Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of property	20 years
Maximum [Member] | Land, Buildings and Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of property	40 years
Maximum [Member] | Leasehold Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of property	20 years