Employee Benefits (Other Comprehensive Income - Retirement Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss	$ 12,110	$ 5,898	$ (12,634)
Amortization of:
Net loss	(3,415)	(6,387)	(6,776)
Prior service benefit	8,740	9,657	9,657
Retirement Income Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss	14,112	10,848	(4,265)
Amortization of:
Net loss	(5,022)	(7,531)	(7,572)
Prior service benefit	3,467	3,467	3,467
Total recognized in other comprehensive income	12,557	6,784	(8,370)
Other Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss	1,624	(1,087)	2,217
Amortization of:
Net loss	(770)	(1,022)	(882)
Prior service benefit	39	39	39
Total recognized in other comprehensive income	$ 893	$ (2,070)	$ 1,374