Accumulated Other Comprehensive Income (Loss) (Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax		$ 1,136	$ 0	$ 6,855	$ 0
Amortization of actuarial losses and prior service cost		(2,730)	(3,476)	(8,192)	(10,427)
Total before taxes		(2,745)	(3,495)	(8,235)	(10,486)
Amounts reclassified from accumulated other comprehensive income, net of tax		5,933	7,698	14,926	16,526
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		(15)	(19)	(43)	(59)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax		631	804	1,894	2,412
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax		(2,114)	(2,691)	(6,341)	(8,074)
Other Comprehensive Income (Loss) Reclassification Adjustment Of Unrealized Losses From AOCI For Securities Available For Sale Transferred To Held To Maturity Before Tax		(6,095)	(6,502)	(18,004)	(10,975)
Other Comprehensive Income (Loss) Reclassification Adjustment Of Unrealized Losses From AOCI For Securities Available For Sale Transferred To Held To Maturity Tax		1,402	1,495	4,141	2,523
Other Comprehensive Income (Loss) Reclassification Adjustment Of Unrealized Losses From AOCI For Securities Available For Sale Transferred To Held To Maturity Net Of Tax		(4,693)	(5,007)	(13,863)	(8,452)
Tax effect		262	0	1,577	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax		874		5,278
Unrealized Losses on Investment Securities Available for Sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive income, net of tax	[1]	(874)	0	(5,278)	0
Defined Benefit Pension Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive income, net of tax	[1]	$ 2,114	$ 2,691	$ 6,341	$ 8,074

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