Employee Benefits (Other Comprehensive Income, Other Postretirement Benefit 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:
Prior service benefit	8,740	9,657	9,657
Net gain	(3,415)	(6,387)	(6,776)
Other Postretirement Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss	(3,626)	(3,863)	(10,586)
Amortization of:
Prior service benefit	5,234	6,151	6,151
Net gain	2,377	2,166	1,678
Total recognized in other comprehensive income	$ 3,985	$ 4,454	$ (2,757)