Note 9 - Retirement Plans - Estimated Rate of Increase in Compensation Levels (Details)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Weighted-average assumptions used to determine net periodic benefit cost for the Gray Pension Plan:
Discount rate	3.55%	4.11%
Expected long-term rate of return on pension plan assets	7.00%	7.00%
Estimated rate of increase in compensation levels
Weighted-average assumptions used to determine benefit obligations:
Discount rate	4.16%	3.55%

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

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Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

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Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

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Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

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