Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Taxes [Line Items]
Effective income tax rate			66.80%	29.30%
Income tax expense	$ (212,379,000)	$ 48,328,000	$ (116,368,000)	$ 162,274,000
Interest or penalties accrued for uncertain tax positions	$ 0		$ 0
Prior Period Adjustments
Income Taxes [Line Items]
Income tax expense				$ 16,100,000