Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			40 years
Depreciation expense from operation	$ 10.7	$ 9.0	$ 20.9	$ 17.5
Real estate cost capitalized excluding interest cost	2.5	2.2	4.7	3.9
Real estate interest cost capitalized incurred	1.8	1.1	3.4	2.1
In Place Leases [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of lease cost	0.6	0.4	1.3	1.0
Tenant Relationship [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of lease cost	$ 0.3	$ 0.4	$ 0.7	$ 0.8
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