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Real Estate and Intangible Assets - Fair Value of Acquired Assets and Liabilities Assumed (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Business Acquisition [Line Items] |  |
Total Purchase Price on all Acquisitions | $ 132,157 | $ 66,570
Business Combinations |  |
Business Acquisition [Line Items] |  |
Total Purchase Price on all Acquisitions | 0 | 40,900
Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Fair Value of Interest rates assumed and (below market leases) |  | 0
Discount on Assumed Debt | 399 | 0
Total Purchase Price on all Acquisitions |  | 25,670
Customer Relationships | Business Combinations |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 0 | 3,090
Customer Relationships | Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 10,806 | 1,406
Above Market Leases | Business Combinations |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 0 | 0
Above Market Leases | Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 3,824 | 188
Below Market Leases | Business Combinations |  |
Business Acquisition [Line Items] |  |
Fair Value of Interest rates assumed and (below market leases) | 0 | 281
Below Market Leases | Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Fair Value of Interest rates assumed and (below market leases) | 2,101 | 0
Land | Business Combinations |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 0 | 7,125
Land | Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 21,509 | 3,681
Building | Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 68,617 | 11,682
Building and Improvements | Business Combinations |  |
Business Acquisition [Line Items] |  |
Total Purchase Price |  | 22,934
Tenant Improvements | Business Combinations |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 0 | 3,240
Tenant Improvements | Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 9,977 | 4,057
In-Place Leases | Business Combinations |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 0 | 3,355
In-Place Leases | Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 12,018 | 2,669
Leasing Costs | Business Combinations |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 0 | 1,437
Leasing Costs | Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Total Purchase Price | 7,066 | $ 1,987
Interest Rate Swap | Asset Acquisitions |  |
Business Acquisition [Line Items] |  |
Fair Value of Interest rates assumed and (below market leases) | $ 42 |

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