Employee Benefits (Other Comprehensive Income - Retirement Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss	$ 5,898	$ (12,634)	$ 20,053
Prior service benefit	0	0	(32,697)
Amortization of:
Net loss	(6,387)	(6,776)	(4,965)
Prior service benefit	9,657	9,657	7,407
Retirement Income Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss	10,848	(4,265)	8,644
Amortization of:
Net loss	(7,531)	(7,572)	(6,554)
Prior service benefit	3,467	3,467	3,467
Total recognized in other comprehensive income	6,784	(8,370)	5,557
Other Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss	(1,087)	2,217	1,266
Amortization of:
Net loss	(1,022)	(882)	(785)
Prior service benefit	39	39	39
Total recognized in other comprehensive income	$ (2,070)	$ 1,374	$ 520