Amount before accumulated depreciation of building structures held for productive use including addition, improvement, or renovation to the structure, including, but not limited to, interior masonry, interior flooring, electrical, and plumbing.

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Real Estate - Allocation of Purchase Prices to Acquired Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real Estate Properties [Line Items]
Land	$ 453,322
Buildings	1,292,631
Total Purchase Price	$ 2,081,597	$ 1,948,165	$ 1,803,200	$ 1,700,813
Ashbrook Marketplace
Real Estate Properties [Line Items]
Land		8,776
Buildings		0
Total Purchase Price		8,776
Ashbrook Marketplace \| In-place Leases
Real Estate Properties [Line Items]
Intangible assets		0
Ashbrook Marketplace \| Above Market Rent
Real Estate Properties [Line Items]
Intangible assets		0
Ashbrook Marketplace \| Below Market Rent
Real Estate Properties [Line Items]
Intangible assets		0
7316 Wisconsin Avenue
Real Estate Properties [Line Items]
Land		38,662
Buildings		979
Total Purchase Price		40,674
7316 Wisconsin Avenue \| In-place Leases
Real Estate Properties [Line Items]
Intangible assets		(886)
7316 Wisconsin Avenue \| Above Market Rent
Real Estate Properties [Line Items]
Intangible assets		(168)
7316 Wisconsin Avenue \| Below Market Rent
Real Estate Properties [Line Items]
Intangible assets		(21)
2018 Acquisitions
Real Estate Properties [Line Items]
Land		47,438
Buildings		979
Total Purchase Price		49,450
2018 Acquisitions \| In-place Leases
Real Estate Properties [Line Items]
Intangible assets		(886)
2018 Acquisitions \| Above Market Rent
Real Estate Properties [Line Items]
Intangible assets		(168)
2018 Acquisitions \| Below Market Rent
Real Estate Properties [Line Items]
Intangible assets		$ (21)