Derivative Instruments and Fair Value Measurements - Summary of Financial Instruments Not Recorded at Fair Value (Detail) $ in Thousands |
Sep. 30, 2018
USD ($)
|
|---|---|
| Carrying Amount | |
| Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | |
| Senior Notes | $ 84,411 |
| Fair Value | |
| Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | |
| Senior Notes | $ 82,855 |