Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2020	$ 4,297,620	$ 334,523	$ 2,894,471	$ 1,205,395	$ 22,370	$ (159,139)
Beginning Balance, shares at Dec. 31, 2020		133,809,374
Net income	106,898	$ 0	0	106,898	0	0
Other comprehensive income (loss), net of tax	(20,509)	0	0	0	(20,509)	0
Total comprehensive income (loss), net of tax	86,389
Stock based compensation expense	1,688	0	1,688	0	0	0
Purchase of treasury stock	(11,210)	0	0	0	0	(11,210)
Cash dividends	(45,254)	0	0	(45,254)	0	0
Net issuance of common stock under stock-based compensation plans	3,465	$ 817	2,648	0	0	0
Net issuance of common stock under stock-based compensation plans, shares		326,522
Ending Balance at Mar. 31, 2021	4,332,698	$ 335,340	2,898,807	1,267,039	1,861	(170,349)
Ending Balance, shares at Mar. 31, 2021		134,135,896
Beginning Balance at Dec. 31, 2020	4,297,620	$ 334,523	2,894,471	1,205,395	22,370	(159,139)
Beginning Balance, shares at Dec. 31, 2020		133,809,374
Net income	201,734
Other comprehensive income (loss), net of tax	(11,847)
Total comprehensive income (loss), net of tax	189,887
Ending Balance at Jun. 30, 2021	4,393,713	$ 335,414	2,901,591	1,316,607	10,523	(170,422)
Ending Balance, shares at Jun. 30, 2021		134,165,663
Beginning Balance at Mar. 31, 2021	4,332,698	$ 335,340	2,898,807	1,267,039	1,861	(170,349)
Beginning Balance, shares at Mar. 31, 2021		134,135,896
Net income	94,836	$ 0	0	94,836	0	0
Other comprehensive income (loss), net of tax	8,662	0	0	0	8,662	0
Total comprehensive income (loss), net of tax	103,498
Stock based compensation expense	1,892	0	1,892	0	0	0
Cash dividends	(45,268)	0	0	(45,268)	0	0
Stock grant forfeiture	0	0	73	0	0	(73)
Net issuance of common stock under stock-based compensation plans	893	$ 74	819	0	0	0
Net issuance of common stock under stock-based compensation plans, shares		29,767
Ending Balance at Jun. 30, 2021	4,393,713	$ 335,414	2,901,591	1,316,607	10,523	(170,422)
Ending Balance, shares at Jun. 30, 2021		134,165,663
Beginning Balance at Dec. 31, 2021	4,718,628	$ 353,402	3,149,955	1,390,777	(4,888)	(170,618)
Beginning Balance, shares at Dec. 31, 2021		141,360,266
Net income	81,664	$ 0	0	81,664	0	0
Other comprehensive income (loss), net of tax	(136,804)	0	0	0	(136,804)	0
Total comprehensive income (loss), net of tax	(55,140)
Stock based compensation expense	2,061	0	2,061	0	0	0
Purchase of treasury stock	(26,061)	0	0	0	0	(26,061)
Cash dividends	(49,266)	0	0	(49,266)	0	0
Stock grant forfeiture	0	0	223	0	0	(223)
Net issuance of common stock under stock-based compensation plans	4,918	$ 1,056	3,862	0	0	0
Net issuance of common stock under stock-based compensation plans, shares		422,766
Ending Balance at Mar. 31, 2022	4,595,140	$ 354,458	3,156,101	1,423,175	(141,692)	(196,902)
Ending Balance, shares at Mar. 31, 2022		141,783,032
Beginning Balance at Dec. 31, 2021	4,718,628	$ 353,402	3,149,955	1,390,777	(4,888)	(170,618)
Beginning Balance, shares at Dec. 31, 2021		141,360,266
Net income	177,277
Other comprehensive income (loss), net of tax	(242,469)				(242,469)
Total comprehensive income (loss), net of tax	(65,192)
Ending Balance at Jun. 30, 2022	4,487,050	$ 354,616	3,159,928	1,470,244	(247,357)	(250,381)
Ending Balance, shares at Jun. 30, 2022		141,846,451
Beginning Balance at Mar. 31, 2022	4,595,140	$ 354,458	3,156,101	1,423,175	(141,692)	(196,902)
Beginning Balance, shares at Mar. 31, 2022		141,783,032
Net income	95,613	$ 0	0	95,613	0	0
Other comprehensive income (loss), net of tax	(105,665)	0	0	0	(105,665)	0
Total comprehensive income (loss), net of tax	(10,052)
Stock based compensation expense	2,543	0	2,543	0	0	0
Purchase of treasury stock	(53,391)	0	0	0	0	(53,391)
Cash dividends	(48,544)	0	0	(48,544)	0	0
Stock grant forfeiture	0		88	0	0	(88)
Net issuance of common stock under stock-based compensation plans	1,354	$ 158	1,196	0	0	0
Net issuance of common stock under stock-based compensation plans, shares		63,419
Ending Balance at Jun. 30, 2022	$ 4,487,050	$ 354,616	$ 3,159,928	$ 1,470,244	$ (247,357)	$ (250,381)
Ending Balance, shares at Jun. 30, 2022		141,846,451