Long-Term Incentive Plans - Additional Information (Detail) $ / shares in Units, $ in Millions	9 Months Ended
Sep. 30, 2020 USD ($) $ / shares
TSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 0.4
Weighted-average period of unrecognized compensation cost	1 year 6 months
PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 0.1
Weighted-average period of unrecognized compensation cost	1 year 6 months
Decrease in share targets \| $ / shares	$ 0.25
PSUs [Member] \| Market Vesting Date [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units vesting percentage	50.00%
PSUs [Member] \| First Anniversary Market-Vesting Date [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units vesting percentage	25.00%
PSUs [Member] \| Second Anniversary Market-Vesting Date [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units vesting percentage	25.00%
Restricted Stock Units (RSUs) [Member] \| 2017 Non-Employee Directors Compensation Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period of unrecognized compensation cost	1 year 6 months
Restricted Stock Units (RSUs) [Member] \| 2017 Non-Employee Directors Compensation Plan [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 0.1

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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

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-Publisher FASB
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- Definition

Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

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+ References

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