Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Taxes [Line Items]
Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Income tax expense (benefit)	$ (134,781)	$ 93,522	$ (174,390)	$ 230,455
Deferred compensation plan
Income Taxes [Line Items]
Income tax expense (benefit)	(2,600)		(3,500)
Valuation Allowance, Operating Loss Carryforwards | Federal
Income Taxes [Line Items]
Income tax expense (benefit)	28,500		28,500
Valuation Allowance, Operating Loss Carryforwards | State
Income Taxes [Line Items]
Income tax expense (benefit)	$ 8,500		$ 19,800