Note 14 - Benefit Plans - Fair Value of Pension Plan's Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair values of the Pension Plan's assets	$ 61,870	$ 58,014	$ 46,488
Fair Value, Inputs, Level 1 [Member]
Fair values of the Pension Plan's assets	51,736	48,314
Fair Value, Inputs, Level 3 [Member]
Fair values of the Pension Plan's assets	10,134	9,700
Mutual Fund [Member]
Fair values of the Pension Plan's assets	51,736	48,314
Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member]
Fair values of the Pension Plan's assets	51,736	48,314
Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member]
Fair values of the Pension Plan's assets
Other Investment [Member]
Fair values of the Pension Plan's assets	10,134	9,700
Other Investment [Member] | Fair Value, Inputs, Level 1 [Member]
Fair values of the Pension Plan's assets
Other Investment [Member] | Fair Value, Inputs, Level 3 [Member]
Fair values of the Pension Plan's assets	$ 10,134	$ 9,700	$ 8,628