Other Comprehensive Income (Loss) (Components Of Comprehensive Income (Loss) In The Consolidated Statements Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total, Before Tax	$ 122,324	$ 102,306	$ 426,931	$ 573,412
Total, Tax Effect	(7,863)	(11,133)	(43,485)	(64,584)
Total, Net of Tax	114,461	91,173	383,446	508,828
URA(D) On Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	68,264	103,247	373,990	587,930
Tax Effect	(4,784)	(9,529)	(38,155)	(61,792)
Net of Tax	63,480	93,718	335,835	526,138
Reclassification, Before Tax	(12,678)	(74)	18,650	(3,597)
Reclassification, Tax Effect	1,225	(455)	(5,961)	(623)
Reclassification, Net of Tax	(11,453)	(529)	12,689	(4,220)
Total, Net of Tax	52,027	93,190	348,524	521,919
URA(D) On Securities OTTI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax		72		(1,671)
Tax Effect		(25)		122
Net of Tax		47		(1,549)
Total, Net of Tax		47		(1,549)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	64,453	(2,665)	28,555	(13,890)
Tax Effect	(3,825)	(761)	1,835	(1,316)
Net of Tax	60,628	(3,426)	30,390	(15,206)
Total, Net of Tax	60,628	(3,426)	30,390	(15,206)
Benefit Plan Net Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification, Before Tax	2,285	1,726	5,736	4,640
Reclassification, Tax Effect	(479)	(363)	(1,204)	(975)
Reclassification, Net of Tax	1,806	1,363	4,532	3,665
Total, Net of Tax	$ 1,806	$ 1,363	$ 4,532	$ 3,665