Tax Effect of Significant Temporary Differences Representing Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 375,308	$ 324,389
Tax credits	4,138	6,404
Expense associated with stock options and restricted stock	10,561	13,375
Workers' compensation allowance	19,536	19,900
Other deferred tax asset	21,698	22,423
Total deferred tax assets, gross	431,241	386,491
Total deferred tax assets, net	414,010	373,259
Valuation allowance	(17,231)	(13,232)
Deferred tax liabilities:
Property and equipment basis difference	(607,785)	(669,196)
Other	(9,184)	(10,224)
Total deferred tax liabilities	(616,969)	(679,420)
Net deferred tax liability	$ (202,959)	$ (306,161)