Quarterly report pursuant to Section 13 or 15(d)

Income Taxes - Additional Information (Detail)

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Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2017
Income Tax Contingency [Line Items]    
Effective corporate income tax rate 21.00% 35.00%
Deferred tax assets, valuation allowance $ 5.4  
Domestic Tax Authority [Member]    
Income Tax Contingency [Line Items]    
Net operating loss carryforwards for federal income tax purpose $ 148.1  
Beginning year of expiry for net operating loss carry forwards 2021  
Ending year of expiry for net operating loss carryforwards 2038  
State and Local Jurisdiction [Member]    
Income Tax Contingency [Line Items]    
Net operating loss carryforwards for federal income tax purpose $ 783.8  
Beginning year of expiry for net operating loss carry forwards 2019  
Ending year of expiry for net operating loss carryforwards 2038