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Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
 9 Months Ended 12 Months Ended
Dec. 31, 2017
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2018
Income Tax [Line Items]        
Increased in valuation allowance against deferred tax assets   $ 2.2    
Increase related to prior tax positions   4.2    
Accrued interest on uncertain tax position   0.0 $ 0.0 $ 0.0
Accrued penalties on uncertain tax position   $ 0.0 0.0 $ 0.0
Federal corporate tax rate 35.00% 21.00%    
Deductibility percentage of certain capital expenditures   100.00%    
Tax benefit from change in corporate tax rates on deferred tax liabilities $ 61.7      
Income tax benefit carryback under CARES Act   $ 35.9    
Net operating losses carryback term due to CARES Act   5 years    
Income tax benefit partially offset created by CARES Act   $ 4.2    
State Income Tax [Member]        
Income Tax [Line Items]        
Net operating loss carryforwards   5.4 1.0  
State Income Tax [Member] | Research and Development (R&D) [Member]        
Income Tax [Line Items]        
Income tax credit   $ 2.2 $ 2.0  
Tax credit carryforward term   20 years