Schedule III - Real Estate and Accumulated Depreciation (Parenthetical) (Detail) $ in Billions	12 Months Ended
	Dec. 31, 2017 USD ($)
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Aggregate cost of land, building and improvements for federal income tax purpose	$ 2.2
Building [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Life upon Which Depreciation is Computed	25 years
Building [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Life upon Which Depreciation is Computed	40 years
Site Improvement [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Life upon Which Depreciation is Computed	5 years
Site Improvement [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Life upon Which Depreciation is Computed	15 years
Tenant Improvements [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Life upon which depreciation is computed, description	shorter of the estimated useful life or non-cancelable term of lease