Note 6 - Accrued Retirement Benefits - Fair Values of Pension Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets	$ 8,120	$ 9,884
Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets	$ 8,120	$ 9,884
Fixed Income Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Fixed Income Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets	$ 46,069	$ 51,483
Fixed Income Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets	$ 46,069	$ 51,483
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets	$ 2,245	$ 2,974
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets	$ 2,245	$ 2,974
Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets	$ 56,434	$ 64,341
Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets	56,434	64,341
Fair value of pension plan assets	$ 56,434	$ 64,341