Accumulated Other Comprehensive Income (Loss) (Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized gains and losses on available for sale securities reclassified from AOCI before tax		$ 1,337	$ 352	$ 4,664	$ 17,509
Amortization of actuarial losses and prior service cost		(2,277)	(1,714)	(7,132)	(5,144)
Total before taxes		(2,330)	(1,768)	(7,290)	(5,302)
Amounts reclassified from accumulated other comprehensive income, net of tax		624	965	1,650	(7,617)
Unrealized gains and losses on available for sale securities reclassified from AOCI tax		(495)	(191)	(1,726)	(6,583)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax		842	161	2,938	10,926
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		(53)	(54)	(158)	(158)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax		864	642	2,702	1,993
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax		(1,466)	(1,126)	(4,588)	(3,309)
Unrealized Loss on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive income, net of tax	[1]	0	0	0	0
Unrealized Gains 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]	(842)	(161)	(2,938)	(10,926)
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]	$ 1,466	$ 1,126	$ 4,588	$ 3,309

[1] All amounts are net of tax.