Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Deferred tax assets, Net operating loss carryforwards	$ 549,166	$ 604,423
Deferred tax assets, Canadian net operating loss carryforwards	19,633	19,341
Deferred tax assets, Alternative minimum tax carryforwards	0	7,781
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	13,122	12,962
Deferred Tax Assets, Other	13,622	21,885
Total deferred tax assets	595,543	666,392
Deferred Tax Assets, Valuation Allowance	(19,633)	(19,341)
Deferred Tax Assets, Net	575,910	647,051
Deferred tax liabilities, Property and equipment	(2,144,767)	(1,903,451)
Deferred Tax Liabilities, Other	(5,579)	(3,158)
Total deferred tax liabilities	(2,150,346)	(1,906,609)
Net deferred tax liabilities	$ (1,574,436)	$ (1,259,558)