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Stock-based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 9 Months Ended
Apr. 30, 2021
May 31, 2020
Sep. 30, 2021
Sep. 30, 2021
Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Number of stock option granted       0 0
Performance Units Awards          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Performance period       3 years  
Unrecognized compensation cost     $ 8.1 $ 8.1  
Weighted-average remaining vesting period       1 year 8 months 12 days  
Performance Units Awards | 2018          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares issued 621,400        
Performance Units Awards | Condition One [Member]          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Award description       The performance goals for the Performance Units are tied to our total shareholder return for the performance period as compared to total shareholder return for a peer group determined by the Compensation Committee. For the performance units granted in April 2021, the peer group also includes three market indices. These goals are considered to be market conditions under the relevant accounting standards and the market conditions were factored into the determination of the fair value of the respective Performance Units. Under the Performance Units granted beginning in April 2019, the recipients will receive the target number of shares if our total shareholder return during the performance period, when compared to the peer group, is at the 55th percentile. If our total shareholder return during the performance period, when compared to the peer group, is at the 75th percentile or higher, then the recipients will receive two times the target number of shares. If our total shareholder return during the performance period, when compared to the peer group, is at the 25th percentile, then the recipients will only receive one-half of the target number of shares. If our total shareholder return during the performance period, when compared to the peer group, is between the 25th and 55th percentile, or the 55th and 75th percentile, then the shares to be received by the recipients will be determined using linear interpolation for levels of achievement between these points. Under the Performance Units granted beginning in April 2019, the payout shall not exceed the target number of shares if our total shareholder return is negative or zero. Additionally, the Performance Units granted in April 2020 will not pay out if our total shareholder return is not equal to or greater than the total stockholder return of the S&P 500 Index for the Performance Period.  
Phantom Share Units (PSUs)          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Award description       Mr. Hendricks may earn from 0% to 200% of a target award of 298,500 phantom units based on our achievement of the same performance conditions over the same Performance Period that applies to the Performance Units granted in April 2020, as described above. Earned Phantom Units, if any, will be settled in 2023, following completion of the three-year Performance Period, in a cash payment equal to the number of earned phantom units multiplied by our average trading price per share over the twenty consecutive trading days ending March 31, 2023.  
Performance completion year   2023      
Performance Period   3 years      
Grant date fair value   $ 1.2      
Expense recognized     0.2 $ 1.3 $ 0.2
Phantom Share Units (PSUs) | Chief Executive Officer and President          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Number of units awardable based on performance conditions   298,500      
Phantom Share Units (PSUs) | Chief Executive Officer and President | Minimum          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Percentage of target award vesting rights   0.00%      
Phantom Share Units (PSUs) | Chief Executive Officer and President | Maximum          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Percentage of target award vesting rights   200.00%      
Restricted Stock Units (RSUs)          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Unrecognized compensation cost     $ 20.9 $ 20.9  
Weighted-average remaining vesting period       1 year 10 months 2 days  
Two Thousand Twenty One Long Term Incentive Plan          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares authorized for grant     13,500,000 13,500,000  
Amended and Restated Plan          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares authorized for grant     4,900,000 4,900,000