Annual report pursuant to Section 13 and 15(d)

Summary of Principal Components of Net Deferred Income Tax Liability (Detail)

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Summary of Principal Components of Net Deferred Income Tax Liability (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Income Tax Disclosure [Abstract]    
Deferred income taxes $ 0 $ 1,424
Deferred Tax Assets, Operating Loss Carryforwards 180,531 175,221
Total net deferred tax assets 8,266 81,906
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Asset Retirement Obligations 1,188 1,073
Deferred Tax Liabilities, Property, Plant and Equipment 7,728 83,330
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Postretirement Benefits 301 340
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost 467 880
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax 0 1,236
Deferred Tax Liabilities, ROU Obligations 538 0
Less:  Valuation allowance (179,006) (114,939)
Deferred Tax Asset, Interest Carryforward 0 11,463
Deferred Tax Assets, Other 1,484 2,441
Deferred Tax Assets, ROU Assets 564 0
Deferred Tax Assets, Gross 187,272 196,845
Deferred Tax Assets, Derivative Instruments 2,737 4,191
Deferred Tax and Other Liabilities, Noncurrent $ 8,266 $ 83,330