Retirement Plans - Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Pension plan
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net loss (gain)	$ 253	$ (355)
Recognition of net actuarial gain or (loss)	(64)	(137)
Recognized prior service cost	0	61
Total changes	189	(431)
Changes, net of taxes	136	(259)
SERP
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net loss (gain)	109	(101)
Recognition of net actuarial gain or (loss)	(66)	(212)
Total changes	43	(313)
Changes, net of taxes	$ 31	$ 188

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Amount, before tax, of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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