Employee Benefits (Components fo net Periodic benefit cost) (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	$ 0	$ 0	$ 0
Interest Cost	4,401	4,193	4,665
Expected Return on Plan Assets	(4,993)	(5,122)	(5,011)
Amortization of Prior Service Credit	0	0	0
Amortization of Net Actuarial Losses (Gains)	1,937	2,099	1,817
Net Periodic Benefit Cost	$ 1,345	$ 1,170	$ 1,471
Weighted average assumptions used to determine the benefit obligations
Discount Rate (as a percent)	3.36%	4.41%
Weighted average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	4.41%	3.90%	4.45%
Expected Long-Term Rate of Return on Plan Assets (as a percent)	5.75%	5.75%	5.75%
Health Care Cost Trend Rate (as a percent)	0.00%	0.00%	0.00%
A one percent change in the health care cost trend rate assumption impact on cost
Expected future employer contributions, next fiscal year	$ 400
Expected benefits to be paid in each of the next five years and in the aggregate for the five years thereafter
2019	7,073
2020	7,215
2021	7,229
2022	7,238
2023	7,240
Years 2024-2028	35,104
Postretirement Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	455	$ 457	$ 453
Interest Cost	1,025	936	1,093
Expected Return on Plan Assets	0	0	0
Amortization of Prior Service Credit	(288)	(567)	(322)
Amortization of Net Actuarial Losses (Gains)	(339)	(264)	(435)
Net Periodic Benefit Cost	$ 853	$ 562	$ 789
Weighted average assumptions used to determine the benefit obligations
Discount Rate (as a percent)	3.42%	4.48%
Health Care Cost Trend Rate Assumed, Next Fiscal Year	5.70%	6.00%
Ultimate health care cost trend rate (as a percent)	4.50%
Weighted average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	4.48%	3.96%	4.57%
Expected Long-Term Rate of Return on Plan Assets (as a percent)	0.00%	0.00%	0.00%
Health Care Cost Trend Rate (as a percent)	6.00%	6.30%	6.50%
A one percent change in the health care cost trend rate assumption impact on cost
Expected future employer contributions, next fiscal year	$ 1,000
Expected benefits to be paid in each of the next five years and in the aggregate for the five years thereafter
2019	1,027
2020	1,064
2021	1,146
2022	1,224
2023	1,332
Years 2024-2028	$ 8,612