Pension and Other Post-Retirement Benefits Benefit Plan Obligation Table (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	$ 13,826,000	$ 14,473,000	$ 13,542,000
Defined Benefit Plan, Service Cost	322,000	335,000	376,000
Defined Benefit Plan, Interest Cost	504,000	511,000	541,000
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(1,196,000)	384,000
Defined Benefit Plan, Benefit Obligation, Benefits Paid	425,000	462,000
Defined Benefit Plan, Fair Value of Plan Assets	8,650,000	9,460,000	8,345,000
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	(544,000)	1,402,000
Defined Benefit Plan, Plan Assets, Contributions by Employer	11,000	12,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(5,176,000)	(5,013,000)
Pension And Other Postretirement Defined Benefit Plans Non-Current Assets	0	0
Liability, Defined Benefit Plan, Current	0	0
Liability, Defined Benefit Plan, Noncurrent	(5,176,000)	(5,013,000)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(5,176,000)	(5,013,000)
Defined Benefit Plan, Plan Assets, Benefits Paid	425,000	462,000
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	148,000	163,000
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	148,000
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	82,947,000	88,598,000	79,307,000
Defined Benefit Plan, Service Cost	1,950,000	1,927,000	1,895,000
Defined Benefit Plan, Interest Cost	3,110,000	3,201,000	3,212,000
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(7,853,000)	7,533,000
Defined Benefit Plan, Benefit Obligation, Benefits Paid	2,750,000	3,295,000
Defined Benefit Plan, Plan Assets, Administration Expense	(108,000)	(75,000)
Defined Benefit Plan, Fair Value of Plan Assets	70,348,000	73,112,000	$ 62,679,000
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	(3,713,000)	10,832,000
Defined Benefit Plan, Plan Assets, Contributions by Employer	3,807,000	2,971,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(12,599,000)	(15,486,000)
Pension And Other Postretirement Defined Benefit Plans Non-Current Assets	0	0
Liability, Defined Benefit Plan, Current	0	0
Liability, Defined Benefit Plan, Noncurrent	(12,599,000)	(15,486,000)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(12,599,000)	(15,486,000)
Defined Benefit Plan, Plan Assets, Benefits Paid	$ 2,750,000	$ 3,295,000