Mortgages and Notes Payable - Summary of Mortgages and Notes Payable (Parenthetical) (Detail) |
12 Months Ended |
|---|---|
Dec. 31, 2017 | |
| Commercial Mortgage Rate | |
| Line Of Credit Facility [Line Items] | |
| Term of note | 5 years |
| Minimum | |
| Line Of Credit Facility [Line Items] | |
| Term of note | 59 months |
| Maximum | |
| Line Of Credit Facility [Line Items] | |
| Term of note | 239 months |
| M&T Bank | 1 Month LIBOR | New York State Energy Research and Development Authority Program | |
| Line Of Credit Facility [Line Items] | |
| Blended interest rate | 1.64% |