Accumulated Other Comprehensive Income (Loss) (Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses and prior service cost		$ (2,741)	$ (3,317)
Total before taxes		(2,755)	(3,337)
Amounts reclassified from accumulated other comprehensive income, net of tax		6,712	2,569
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		(14)	(20)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax		634	768
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax		(2,121)	(2,569)
Other Comprehensive Income (Loss) Reclassification Adjustment Of Unrealized Losses From AOCI For Securities Available For Sale Transferred To Held To Maturity Before Tax		(5,962)
Other Comprehensive Income (Loss) Reclassification Adjustment Of Unrealized Losses From AOCI For Securities Available For Sale Transferred To Held To Maturity Tax		1,371
Other Comprehensive Income (Loss) Reclassification Adjustment Of Unrealized Losses From AOCI For Securities Available For Sale Transferred To Held To Maturity Net Of Tax		(4,591)
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]	0	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]	$ 2,121	$ 2,569

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