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 | |