Note 12 - Long-term Debt - Summary of Long-term Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Long-term debt	$ 55	$ 100
Less current portion
Long-term debt, noncurrent	$ 55	100
Line of Credit [Member]
Long-term debt, weighted average interest rate	3.90%
Long-term debt, maturities	2020
Long-term debt	$ 55	90
Unsecured Term Note Payable [Member]
Long-term debt, maturities	2028
Long-term debt		$ 10