Long-Term Incentive Plans - Summary of Information Regarding Board RSUs Granted (Parenthetical) (Detail) - 2017 Non-Employee Directors Compensation Plan [Member] - Restricted Stock Units (RSUs) [Member] $ / shares in Units, $ in Millions	Sep. 30, 2019 USD ($) $ / shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate grant date fair value of restricted stock units issued | $	$ 0.3
Grant Date Market Price | $ / shares	$ 6.95