v3.8.0.1

Commitments and Contingencies - Additional Information (Detail) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) Agreement | Dec. 31, 2016 USD ($) Agreement
Loss Contingencies [Line Items] |  |
Number of lease agreements assumed in acquisitions | Agreement | 6 | 6
Tenant improvement allowances in acquisitions | $ 2,777 | $ 10,464
Payments for work completed under tenant improvement allowances | 6,598 | 974
Tenant improvement allowances | 5,669 | $ 9,490
Maximum |  |
Loss Contingencies [Line Items] |  |
Maximum aggregate amount | $ 12,300 |

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