Employee Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net loss (gain)		$ 5,093	$ 3,710	$ (3,098)
Prior service credit	[1]	0	(12)	(18)
Recognized in other comprehensive income (loss)		(2,952)	(2,526)	4,981
Qualified Pension Plan [Member]
Net Periodic Benefit Cost:
Service cost	[2]	2,164	2,037	2,244
Interest cost	[3]	2,505	2,967	2,715
Expected return on plan assets	[3]	(4,538)	(4,495)	(5,272)
Amortization of prior service credit	[3]	0	(16)	(23)
Recognized net actuarial loss	[3]	1,582	792	1,496
Net periodic benefit cost		1,713	1,285	1,160
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net loss (gain)		1,708	890	(4,342)
Prior service credit		0	16	23
Recognized in other comprehensive income (loss)		1,708	906	(4,319)
Total recognized in net periodic benefit cost and other comprehensive income (loss)		3,421	2,191	(3,159)
Non-Qualified Retirement Plans [Member]
Net Periodic Benefit Cost:
Service cost	[2]	170	126	108
Interest cost	[3]	465	563	475
Expected return on plan assets	[3]	0	0	0
Amortization of prior service credit	[3]	0	0	(1)
Recognized net actuarial loss	[3]	560	408	411
Net periodic benefit cost		1,195	1,097	993
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (on a pre-tax basis):
Net loss (gain)		1,244	1,620	(663)
Prior service credit		0	0	1
Recognized in other comprehensive income (loss)		1,244	1,620	(662)
Total recognized in net periodic benefit cost and other comprehensive income (loss)		$ 2,439	$ 2,717	$ 331

[1] The pre-tax amounts are included in other expenses in the Consolidated Statements of Income.

[2] Included in salaries and employee benefits expense in the Consolidated Statements of Income.

[3] Included in other expenses in the Consolidated Statements of Income.