Income Taxes - Components of Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ 363,043	$ 428,750	$ 130,349
State and local	94,714	95,426	21,549
Total current	457,757	524,176	151,898
Deferred
Federal	367,308	147,662	324,317
State and local	33,482	26,351	72,279
Total deferred	400,790	174,013	396,596
Amortization of investments in qualified affordable housing projects	57,009	45,095	46,531
Income taxes	$ 915,556	$ 743,284	$ 595,025