Reconciliation of Statutory Federal Income Tax Expense (Benefit) Reported in Net Income to Combined Actual Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Provision of Income Taxes [Line Items]
Statutory federal income tax at 21%, 35% and 35%, respectively	$ 117,111	$ 233,875	$ 271,995
State and local income taxes, net of federal income tax effect	24,451	29,204	30,772
Effect of tax law changes	1,625	(41,943)
Non-deductible FDIC deposit insurance premiums	8,852
Effect of tax deductibility of ESOP	(3,116)	(5,083)	(6,452)
Non-taxable income and expense of BOLI	(5,957)	(9,529)	(10,808)
Federal tax credits	(531)	(1,386)	(1,607)
Adjustments relating to prior tax years	(7,246)	144	(668)
Merger-related expenses			(850)
Other, net	63	(3,268)	(655)
Income tax expense reported in net income	$ 135,252	$ 202,014	$ 281,727