Other Comprehensive Income (Loss) (Components Of Comprehensive Income (Loss) In The Consolidated Statements Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total, Before Tax	$ 639,188	$ 199,401	$ 304,606	$ 471,106
Total, Tax Effect	(72,300)	(28,192)	(35,622)	(53,451)
Total, Net of Tax	566,888	171,209	268,984	417,655
URA(D) On Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	620,926	228,053	305,725	484,683
Tax Effect	(69,173)	(28,872)	(33,371)	(52,263)
Net of Tax	551,753	199,181	272,354	432,420
Reclassification, Before Tax	(6,849)	(787)	31,328	(3,523)
Reclassification, Tax Effect	(408)	(1,082)	(7,186)	(168)
Reclassification, Net of Tax	(7,257)	(1,869)	24,142	(3,691)
Total, Net of Tax	544,496	197,312	296,496	428,729
URA(D) On Securities OTTI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax		(1,499)		(1,743)
Tax Effect		77		147
Net of Tax		(1,422)		(1,596)
Total, Net of Tax		(1,422)		(1,596)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before Tax	22,825	(27,823)	(35,898)	(11,225)
Tax Effect	(2,239)	1,991	5,660	(555)
Net of Tax	20,586	(25,832)	(30,238)	(11,780)
Total, Net of Tax	20,586	(25,832)	(30,238)	(11,780)
Benefit Plan Net Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification, Before Tax	2,286	1,457	3,451	2,914
Reclassification, Tax Effect	(480)	(306)	(725)	(612)
Reclassification, Net of Tax	1,806	1,151	2,726	2,302
Total, Net of Tax	$ 1,806	$ 1,151	$ 2,726	$ 2,302