Parent Company Financial Statements - Condensed Statement of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income	$ 1,858,746	$ 1,353,152	$ 1,929,149
Adjustments to reconcile net income to net cash provided by operating activities
Provision for deferred income taxes	87,159	(31,291)	57,548
Net cash provided by operating activities	2,714,959	789,187	2,357,555
Cash flows from investing activities
Other, net	(510,302)	67,411	(195,921)
Cash flows from financing activities
Purchases of treasury stock		(373,750)	(1,349,785)
Dividends paid — common	(580,260)	(568,112)	(552,138)
Dividends paid — preferred	(68,200)	(68,256)	(67,454)
Redemption of Series A and Series C preferred stock			(381,500)
Proceeds from issuance of Series I and G preferred stock	495,000		396,000
Other, net	(26,710)	(11,413)	(25,393)
Supplemental disclosure of cash flow information
Interest received during the year	3,976,804	4,135,990	4,892,301
Income taxes received during the year	314,295	275,558	320,513
Parent Company [Member]
Cash flows from operating activities
Net income	1,858,746	1,353,152	1,929,149
Adjustments to reconcile net income to net cash provided by operating activities
Equity in undistributed income of subsidiaries	(854,643)	(650,246)	70,946
Provision for deferred income taxes	10,356	1,079	5,263
Net change in accrued income and expense	(23,047)	(24,206)	(34,525)
Net cash provided by operating activities	991,412	679,779	1,970,833
Cash flows from investing activities
Proceeds from sales or maturities of investment securities			100
Net investment in consolidated subsidiaries	(199,000)	125,654
Other, net	(2,777)	50,396	51,235
Net cash provided (used) by investing activities	(201,777)	176,050	51,335
Cash flows from financing activities
Purchases of treasury stock		(373,750)	(1,349,785)
Dividends paid — common	(580,260)	(568,112)	(552,138)
Dividends paid — preferred	(68,200)	(68,256)	(67,454)
Redemption of Series A and Series C preferred stock			(381,500)
Other, net	(7,551)	(5,992)	(4,431)
Net cash used by financing activities	(161,011)	(1,016,110)	(1,959,308)
Net increase (decrease) in cash and cash equivalents	628,624	(160,281)	62,860
Cash and cash equivalents at beginning of year	800,069	960,350	897,490
Cash and cash equivalents at end of year	1,428,693	800,069	960,350
Supplemental disclosure of cash flow information
Interest received during the year	1,165	1,493	1,752
Interest paid during the year	20,457	30,913	49,451
Income taxes received during the year	53,067	$ 11,528	6,251
Parent Company [Member] | Series I and Series G Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of Series I and G preferred stock	$ 495,000		$ 396,000