Retirement Plans - Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Pension plan
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net loss (gain)	$ (60)	$ 253
Recognition of net actuarial gain or (loss)	(75)	(64)
Total changes	(135)	189
Changes, net of taxes	(97)	136
SERP
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net loss (gain)	486	109
Recognition of net actuarial gain or (loss)	(62)	(66)
Total changes	424	43
Changes, net of taxes	$ 305	$ 31

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Amount, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for 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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Amount, before tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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

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