Accumulated Other Comprehensive Loss (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), before Tax		$ (305,438)		$ (193,833)
Deferred tax expense (benefit)		(70,251)		(71,539)
Accumulated other comprehensive income (loss), net of tax		(235,187)		(122,294)		$ (135,192)
Income taxes		(103,297)		(219,946)		(125,585)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(23,667)		(3,419)
Securities gains (losses)		351		4,293		26,673
Unrealized losses on securities available for sale
Accumulated Other Comprehensive Income (Loss), before Tax		(50,007)		(48,834)
Deferred tax expense (benefit)		(11,502)		(17,889)
Accumulated other comprehensive income (loss), net of tax	[2]	(38,505)		(30,945)		(45,875)
Income taxes	[1]	(81)		(1,588)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]	270		2,705
Securities gains (losses)	[1]	351		4,293
Unrealized losses on securities available for sale transferred to held to maturity
Accumulated Other Comprehensive Income (Loss), before Tax		(92,401)		0
Deferred tax expense (benefit)		(21,252)		0
Accumulated other comprehensive income (loss), net of tax	[2]	(71,149)		0		0
Income taxes	[1]	3,934
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[2]	(13,172)	[1]	0
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss), before Tax		(163,030)		(144,999)
Deferred tax expense (benefit)		(37,497)		(53,650)
Accumulated other comprehensive income (loss), net of tax	[2]	(125,533)		(91,349)		$ (89,317)
Income taxes	[1]	3,216		3,596
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]	(10,765)		(6,124)
Employee Benefits, prior service costs	[1]	(79)		(210)
Reclassification adjustment for losses included in income before income taxes	[1]	(13,902)		(9,510)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax		$ (13,981)		$ (9,720)	[1]

[1] Amounts in parentheses indicate debits to profit/loss.

[2] All amounts are net of tax. Amounts in parentheses indicate debits.