Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock Outstanding [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss), Net of Deferred Income Taxes [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2020			$ 696	$ 2,245,301	$ 534,899	$ 10,567,452	$ (3,622,172)
Balance, shares at Dec. 31, 2020		39,983,481
Issued during the period, net, shares		196,481
Treasury shares acquired, shares		(97,462)
Issued during the period, net			2
Share-based compensation plans				436
Net increase (decrease) during the period	$ (299,820)				(299,820)
Net income (loss)	341,862					341,862
Dividends declared ($1.55 per share 2022 and $1.55 per share 2021)	(62,229)					(62,228)
Purchase of treasury shares							(23,545)
Balance at Mar. 31, 2021	9,682,882		698	2,245,737	235,079	10,847,085	(3,645,717)
Balance, shares at Mar. 31, 2021		40,082,500
Balance at Dec. 31, 2021	$ 10,139,180		698	2,274,431	11,523	11,699,836	(3,847,308)
Balance, shares at Dec. 31, 2021	69,790,000	39,266,633
Issued during the period, net, shares		187,044
Treasury shares acquired, shares		(5,000)
Issued during the period, net			2
Share-based compensation plans				(2,541)
Net increase (decrease) during the period	$ (844,343)				(844,343)
Net income (loss)	297,751					297,751
Dividends declared ($1.55 per share 2022 and $1.55 per share 2021)	(61,097)					(61,097)
Purchase of treasury shares							(1,322)
Balance at Mar. 31, 2022	$ 9,527,629		$ 700	$ 2,271,890	$ (832,820)	$ 11,936,489	$ (3,848,630)
Balance, shares at Mar. 31, 2022	69,977,000	39,448,677