Employee Benefits (Components fo net Periodic benefit cost) (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	$ 0	$ 0	$ 0
Interest Cost	4,882	4,655	4,975
Expected Return on Plan Assets	(5,121)	(5,222)	(5,100)
Amortization of Prior Service Credit	0	0	0
Amortization of Net Actuarial Losses (Gains)	1,617	1,713	1,408
Net Periodic Benefit Cost	1,378	$ 1,146	$ 1,283
Estimated amount expected to be amortized from accumulated other comprehensive income (loss) into net periodic benefit cost in next fiscal year
Net actuarial loss	$ 1,700
Weighted average assumptions used to determine the benefit obligations
Discount Rate (as a percent)	4.45%	4.70%
Weighted average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	4.70%	4.25%	5.22%
Expected Long-Term Rate of Return on Plan Assets (as a percent)	6.00%	6.00%	6.00%
Health Care Cost Trend Rate (as a percent)	0.00%	0.00%	0.00%
Expected benefits to be paid in each of the next five years and in the aggregate for the five years thereafter
2015	$ 6,478
2016	6,604
2017	6,842
2018	6,999
2019	7,116
Years 2020-2024	36,099
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year	500
Postretirement Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	513	$ 621	$ 586
Interest Cost	1,134	1,155	1,325
Expected Return on Plan Assets	0	0	0
Amortization of Prior Service Credit	(322)	(322)	(322)
Amortization of Net Actuarial Losses (Gains)	(393)	(89)	(152)
Net Periodic Benefit Cost	932	$ 1,365	$ 1,437
Estimated amount expected to be amortized from accumulated other comprehensive income (loss) into net periodic benefit cost in next fiscal year
Net gain and prior service credit	$ 800
Weighted average assumptions used to determine the benefit obligations
Discount Rate (as a percent)	4.57%	4.74%
Health Care Cost Trend Rate Assumed For Next Year (as a percent)	6.50%	6.70%
Ultimate health care cost trend rate (as a percent)	4.50%
Year that reaches the ultimate health care cost trend rate	2036
Weighted average assumptions used to determine the net periodic benefit cost
Discount rate (as a percent)	4.74%	4.28%	5.22%
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)	6.70%	7.00%	7.20%
A one percent change in the health care cost trend rate assumption impact on cost
Effect of one percentage increase on the total of service and interest cost components of net periodic postretirement benefit cost	$ 144
Effect of one percentage increase on the postretirement benefit obligation	1,516
Effect of one percentage decrease on the total of service and interest cost components of net periodic postretirement benefit cost	(121)
Effect of one percentage decrease on the postretirement benefit obligation	(1,393)
Expected benefits to be paid in each of the next five years and in the aggregate for the five years thereafter
2015	974
2016	951
2017	984
2018	1,049
2019	1,131
Years 2020-2024	7,366
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year	$ 1,000