Real Estate - Additional Information (Detail) |
12 Months Ended |
|---|---|
Dec. 31, 2017 | |
| Real Estate Properties [Line Items] | |
| Weighted average lease term remaining | 48 months |
| Minimum lease payments on leases periods | Greater than one year |
| Minimum [Member] | |
| Real Estate Properties [Line Items] | |
| Operating leases lease term | 1 year |
| Maximum [Member] | |
| Real Estate Properties [Line Items] | |
| Operating leases lease term | 65 years |