Long-Term Incentive Plans - Additional Information (Detail) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2021 USD ($) $ / shares shares
EIP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Future Grants Issuance \| shares	2,802,856
TSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 2.7
Weighted-average period of unrecognized compensation cost	1 year 8 months 12 days
PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period of unrecognized compensation cost	1 year 4 months 24 days
Decrease in share targets \| $ / shares	$ 0.25
PSUs [Member] \| Third Anniversary Vesting [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units vesting percentage	50.00%
PSUs [Member] \| First Anniversary Vesting [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units vesting percentage	25.00%
PSUs [Member] \| Second Anniversary Vesting [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units vesting percentage	25.00%
PSUs [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 0.1
2017 Non-Employee Directors Compensation Plan [Member] \| Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period of unrecognized compensation cost	9 months 18 days
2017 Non-Employee Directors Compensation Plan [Member] \| Maximum [Member] \| Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 0.1
PRSU [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 0.3
Weighted-average period of unrecognized compensation cost	2 years 1 month 6 days
Fair value estimation method	The fair value of each PRSU award was estimated on their grant dates using a Monte Carlo simulation.
PRSU [Member] \| Third Anniversary Vesting [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units vesting percentage	50.00%
PRSU [Member] \| First Anniversary Vesting [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units vesting percentage	25.00%
PRSU [Member] \| Second Anniversary Vesting [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units vesting percentage	25.00%
PRSU [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of Potential Payout	200.00%
PRSU [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of Potential Payout	0.00%

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Percentage of vesting of award under share-based payment arrangement.

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