Other Comprehensive Income (Loss) (Component Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, before Tax	$ 24,200
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	176,007						176,007
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	$ 186						$ 421	$ 2,600
Other comprehensive loss before reclassifications	13,840			$ (5,141)			36,841	(30,919)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	0						0	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	0						0	0
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets										$ (995)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	0			0			0	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	(49)			0			(556)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	(147)			0			333	2,024
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(147)						333	2,024
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	13,742			(5,141)			37,730	(28,895)
Other comprehensive income (loss)	13,693			(5,141)			37,174	(28,895)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments, after Tax	13,889			(5,141)			37,397	(30,919)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax	0			0			0	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	(49)			0			(556)	0
Changes in pension plan assets and benefit obligations, Net-of-tax amount	(29,672)	$ 29,672		(26,701)	$ 26,701		(29,672)	(26,701)	$ 29,672	23,526
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	(556)	(507)		0	0		(556)	0	0	0
Unrealized gains on available-for-sale securities, Net-of-tax amount	17,614	3,872		(33,449)	(28,308)		17,614	(33,449)	(20,116)	(2,928)
Total accumulated other comprehensive income (loss), Net-of-tax amount	(12,614)	(26,307)		(60,150)	(55,009)		$ (12,614)	$ (60,150)	$ (49,788)	(26,454)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, before Tax				0
Accumulated Other Comprehensive Income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets										(3,806)
Other comprehensive income (loss)	$ 13,693	$ 9,146	$ 14,335	$ (5,141)	$ (2,368)	$ (21,386)
Accumulated Other Comprehensive Income (loss) [Member] | Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets										(3,175)
Accumulated Other Comprehensive Income (loss) [Member] | Debt Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets										(631)
Accounting Standards Update 2016-01 [Member] | Accumulated Other Comprehensive Income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets										(995)
Adjustments for New Accounting Pronouncement [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in pension plan assets and benefit obligations, Net-of-tax amount										23,526
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax										0
Unrealized gains on available-for-sale securities, Net-of-tax amount										(3,923)
Total accumulated other comprehensive income (loss), Net-of-tax amount										$ (27,449)