Note 12 - Pension and Other Postretirement Benefit Plans - Benefit Payments, Which Reflect Expected Future Service, Expected to be Paid by the Retirement Plan (Details) - Retirement Plan [Member] $ in Thousands	Dec. 31, 2017 USD ($)
2018	$ 1,421
2019	1,202
2020	1,199
2021	1,238
2022	1,306
2023 – 2027	$ 6,490

Note 12 - Pension and Other Postretirement Benefit Plans - Benefit Payments, Which Reflect Expected Future Service, Expected to be Paid by the Retirement Plan (Details) - Retirement Plan [Member]
$ in Thousands

Dec. 31, 2017

USD ($)

$ 1,421

1,202

1,199

1,238

1,306

$ 6,490