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Tax Effect of Temporary Differences and Tax Attributes Representing Deferred Tax Assets and Liabilities (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Deferred tax assets:    
Net operating loss carryforwards $ 370,875 $ 375,308
Tax credits 4,918 4,138
Expense associated with stock-based compensation 11,252 10,561
Workers' compensation allowance 17,177 19,536
Other deferred tax asset 24,735 21,698
Total deferred tax assets, gross 428,957 431,241
Total deferred tax assets, net 409,824 414,010
Valuation allowance (19,133) (17,231)
Deferred tax liabilities:    
Property and equipment basis difference (475,025) (607,785)
Other (12,475) (9,184)
Total deferred tax liabilities (487,500) (616,969)
Net deferred tax liability $ (77,676) $ (202,959)