Note 14 - Benefit Plans - Reconciliation of Level 3 Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Balance at beginning of period	$ 58,014	$ 46,488
Balance at end of period	61,870	58,014
Fair Value, Inputs, Level 3 [Member]
Balance at beginning of period	9,700
Balance at end of period	10,134	9,700
Other Investment [Member]
Balance at beginning of period	9,700
Balance at end of period	10,134	9,700
Other Investment [Member] | Fair Value, Inputs, Level 3 [Member]
Balance at beginning of period	9,700	8,628
Purchases	3,805
Redemptions	(3,795)
Realized gains	424	1,072
Balance at end of period	$ 10,134	$ 9,700