Condensed Financial Statements of Parent Company (Schedule of Condensed Statements of Cash Flows) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 648,557	$ 582,542	$ 597,973
Stock-based compensation	24,755	19,763	24,590
Net tax benefit from stock-based compensation	2,265	3,795	894
Net cash provided by (used in) operating activities	273,979	989,532	478,845
Net cash provided by (used in) investing activities	(1,601,095)	(180,879)	(942,751)
Proceeds from stock option exercises	11,946	22,643	9,299
Purchase of treasury stock	(157,832)	(60,901)	(42,720)
Cash dividends paid on preferred stock	(6,675)	(6,675)	(6,675)
Cash dividends paid on common stock	(255,356)	(242,446)	(232,323)
Net cash provided by (used in) financing activities	(33,087)	738,329	(2,876,950)
Net change in cash and cash equivalents	(1,360,203)	1,546,982	(3,340,856)
Cash and cash equivalents at beginning of year	10,234,258	8,687,276	12,028,132
Cash and cash equivalents at end of year	8,874,055	10,234,258	8,687,276
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	648,557	582,542	597,973
Equity in undistributed earnings of subsidiaries	(309,823)	(335,724)	(331,761)
Stock-based compensation	1,020	934	880
Net tax benefit from stock-based compensation	393	463	331
Net change in other assets and other liabilities	11,177	4,322	19,867
Net cash provided by (used in) operating activities	351,324	252,537	287,290
Capital contribution to subsidiary	(500)	0	0
Net cash provided by (used in) investing activities	(500)	0	0
Proceeds from stock option exercises	11,946	22,643	9,299
Proceeds from stock-based compensation activities of subsidiaries	23,735	18,829	23,710
Purchase of treasury stock	(157,832)	(60,901)	(42,720)
Cash dividends paid on preferred stock	(6,675)	(6,675)	(6,675)
Cash dividends paid on common stock	(255,356)	(242,446)	(232,323)
Net cash provided by (used in) financing activities	(384,182)	(268,550)	(248,709)
Net change in cash and cash equivalents	(33,358)	(16,013)	38,581
Cash and cash equivalents at beginning of year	334,512	350,525	311,944
Cash and cash equivalents at end of year	$ 301,154	$ 334,512	$ 350,525