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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Total income (loss) before income taxes	$ 72,676	$ (199,692)	$ 56,236	$ 210,015
U.S. federal statutory rate	21.00%	35.00%	21.00%	35.00%
Total tax expense (benefit) at statutory rate	$ 15,262	$ (69,892)	$ 11,810	$ 73,505
State and local income taxes, net of federal benefit	2,691	(6,537)	3,439	6,591
Non-deductible executive compensation	48	296	601	436
Equity compensation	6	56	2,146	4,808
Change in valuation allowances:
Federal net operating loss carryforwards & other	0	69	0	3,487
State net operating loss carryforwards & other	5,558	4,286	19,194	10,498
Rabbi trust and other	100	(508)	1,499	(1,561)
Permanent differences and other	472	238	(394)	290
Total expense (benefit) for income taxes	$ 24,137	$ (71,992)	$ 38,295	$ 98,054
Effective tax rate	33.20%	36.10%	68.10%	46.70%