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
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Total income before income taxes	$ 91,914	$ 282,506
U.S. federal statutory rate	21.00%	35.00%
Total tax expense at statutory rate	$ 19,302	$ 98,877
State and local income taxes, net of federal benefit	4,494	8,982
Non-deductible executive compensation	262	140
Tax less than book equity compensation	664	2,524
Change in valuation allowances:
Federal net operating loss carryforwards & other	0	856
State net operating loss carryforwards & other	15,678	2,086
Rabbi trust and other	1,381	(1,122)
Permanent differences and other	895	52
Total (benefit) expense for income taxes	$ 42,676	$ 112,395
Effective tax rate	46.40%	39.80%