Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, State		$ 3,400,000
Alternative minimum tax credit carryforward		7,780
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	[1]	(404)	$ (1,044)	$ (13,503)
Deferred Tax Assets, Valuation Allowance		19,341	$ 18,936
UNITED STATES
Operating Loss Carryforwards [Line Items]
Federal Operating Loss Carryforwards		2,390,000
OKLAHOMA
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, State		2,170,000
NORTH DAKOTA
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, State		$ 1,070,000

[1] Represents valuation allowances recognized against all deferred tax assets associated with operating loss carryforwards generated by the Company's Canadian operations during the respective periods for which the Company does not expect to realize a benefit.