Income Taxes - Summary of Differences In Effective Tax Rate and Federal Statutory Rate Due to State Income Taxes and Other Tax Items (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Total income (loss) before income taxes	$ 127,201	$ (354,424)	$ 409,707	$ (490,172)
U.S. federal statutory rate	35.00%	35.00%	35.00%	35.00%
Total tax expense (benefit) at statutory rate	$ 44,520	$ (124,048)	$ 143,397	$ (171,560)
State and local income taxes, net of federal benefit	4,146	(11,524)	13,128	(15,956)
Non-deductible executive compensation	0	446	140	682
Tax less than book equity compensation	2,228	64	4,752	5,330
Change in valuation allowances:
Federal net operating loss carryforwards & other	2,562	3,209	3,418	0
State net operating loss carryforwards & other	4,127	2,327	6,212	7,699
Rabbi trust and other	68	0	(1,053)	2,276
Permanent differences and other	0	38	52	65
Total income tax expense (benefit)	$ 57,651	$ (129,488)	$ 170,046	$ (171,464)
Effective tax rate	45.30%	36.50%	41.50%	35.00%