Summary Of Significant Accounting Policies (Components Of Other Comprehensive Income And Related Tax Effects) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in net unrealized holding gains (losses) on available-for-sale securities:
Change arising during the period		$ (18,891)	$ (236)	$ (15,153)
Reclassification adjustment for net losses (gains) included in net income	[1]	10,406	1,867	(1,851)
Change in net unrealized holding gains (losses) on available-for-sale securities		(8,485)	1,631	(17,004)
Tax effect		(2,569)	685	(6,983)
Total		(5,916)	946	(10,021)
Change in funded status of pension plan:
Unrecognized net gain (loss) arising during the period		(4,316)	1,700	1,199
Amortization of net actuarial loss included in pension expense	[2]		18	244
Total		(4,316)	1,718	1,443
Tax effect		(1,312)	514	550
Total		(3,004)	1,204	893
Change in unrealized loss on derivative instrument:
Amount of loss recognized during the period		(1,607)
Reclassification adjustment for net interest expense included in net income	[3]	477
Change in unrealized loss on derivative instruments		(1,130)
Tax effect		(341)
Total		(789)
Other comprehensive income (loss)		$ (9,709)	$ 2,150	$ (9,128)

[1] Represents net realized gains and losses arising from the sale of available-for-sale securities. These net realized gains and losses are included in the consolidated statements of income in the line item, "Net gains (losses) on sales of securities." See "Note B - Investment Securities" for the income tax expense or benefit related to these net realized gains and losses, which is included in the consolidated statements of income in the line item "Income tax expense."

[2] Represents the amortization of net actuarial loss relating to the Corporation's defined benefit pension plan. This item is a component of net periodic pension cost (see "Note J - Retirement Plans") and included in the consolidated statements of income in the line item, "Other noninterest income."

[3] Represents the net interest expense recorded on a derivative transaction and included in the consolidated statements of income in the line item "Interest expense - short-term borrowings."