Income Taxes - Summary of Differences In Effective Tax Rate and Federal Statutory Rate Due to State Income Taxes, Equity Compensation and Other Tax Items (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Total (loss) income before income taxes	$ (108,354)	$ 127,201	$ (16,440)	$ 409,707
U.S. federal statutory rate	21.00%	35.00%	21.00%	35.00%
Total tax (benefit) expense at statutory rate	$ (22,754)	$ 44,520	$ (3,452)	$ 143,397
State and local income taxes, net of federal benefit	(3,745)	4,146	749	13,128
Non-deductible executive compensation	291	0	553	140
Equity compensation	1,476	2,228	2,140	4,752
Change in valuation allowances:
Federal net operating loss carryforwards & other	0	2,562	0	3,418
State net operating loss carryforwards & other	(2,042)	4,127	13,636	6,212
Rabbi trust and other	18	68	1,399	(1,053)
Permanent differences and other	(1,762)	0	(867)	52
Total (benefit) expense for income taxes	$ (28,518)	$ 57,651	$ 14,158	$ 170,046
Effective tax rate	26.30%	45.30%	(86.10%)	41.50%