Parent Company Financial Statements - Condensed Statement of Income (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Expense
Interest on long-term borrowings	$ 109,332	$ 239,242	$ 248,556
Other expense	3,385,240	3,468,682	3,288,062
Income tax credits	(416,369)	(618,112)	(590,160)
Equity in undistributed income of subsidiaries
Net income	$ 1,353,152	$ 1,929,149	$ 1,918,080
Net income per common share
Basic	$ 9.94	$ 13.76	$ 12.75
Diluted	$ 9.94	$ 13.75	$ 12.74
Parent Company [Member]
Income
Dividends from consolidated subsidiaries	$ 708,500	$ 2,025,000	$ 1,250,000
Income from Bayview Lending Group LLC	52,940	36,740	23,500
Other income	5,110	7,216	2,417
Total income	766,550	2,068,956	1,275,917
Expense
Interest on long-term borrowings	31,924	51,938	36,354
Other expense	33,704	25,236	23,894
Total expense	65,628	77,174	60,248
Income before income taxes and equity in undistributed income of subsidiaries	700,922	1,991,782	1,215,669
Income tax credits	1,984	8,313	8,446
Income before equity in undistributed income of subsidiaries	702,906	2,000,095	1,224,115
Equity in undistributed income of subsidiaries
Net income of subsidiaries	1,358,746	1,954,054	1,943,965
Less: dividends received	(708,500)	(2,025,000)	(1,250,000)
Equity in undistributed income of subsidiaries	650,246	(70,946)	693,965
Net income	$ 1,353,152	$ 1,929,149	$ 1,918,080
Net income per common share
Basic	$ 9.94	$ 13.76	$ 12.75
Diluted	$ 9.94	$ 13.75	$ 12.74