Income Taxes - Reconciliation of Difference Between Company's Income Tax Provision Calculated at Federal Statutory Rate and Actual Income Tax Provision (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Provision of Income Taxes [Line Items]
Statutory rate		$ (42,988)	$ (38,274)	$ 37,302
State taxes, net		(1,228)	(1,094)	1,066
Non-deductible expense		3,488	1,070	1,440
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount		15,118
Valuation Allowance, Deferred Tax Asset, Change in Amount		33,100	2,295	(1,011)
Effective Income Tax Rate Reconciliation Income Excluded from U.S. Taxable Income		0	(9,478)	0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 125,225	(125,225)	0	0
Foreign taxes and other		591	(25)	960
Total tax expense (benefit)		$ (150,244)	$ (45,506)	$ 39,757