Retirement Plans, Summary of Expected Federal Subsidy (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Pension Plan [Member]
Expected federal subsidy [Abstract]
Year one	$ 0	$ 0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Next five years	0	0
SERP [Member]
Expected federal subsidy [Abstract]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Next five years	0	0
Other Postretirement Benefits [Member]
Expected federal subsidy [Abstract]
Year one	0	(7)
Year two	0	(6)
Year three	0	(6)
Year four	0	(6)
Year five	0	(7)
Next five years	$ 0	$ (30)

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Amount of prescription drug subsidy receipts expected after fifth fiscal year following latest fiscal year.

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Amount of prescription drug subsidy receipts expected in next fiscal year following latest fiscal year.

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Amount of prescription drug subsidy receipts expected in fifth fiscal year following latest fiscal year.

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Amount of prescription drug subsidy receipts expected in fourth fiscal year following latest fiscal year.

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