Note 8 - Employee Retirement Plans - Pension Plan Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair value of plan assets	$ 56,779	$ 56,495	$ 59,625	$ 56,790
Pension Plan [Member] \| Change In Plan Assets [Member]
Fair value of plan assets	56,779	56,495
Pension Plan [Member] \| Fair Value, Inputs, Level 1 [Member] \| Change In Plan Assets [Member]
Fair value of plan assets	55,868	39,705
Pension Plan [Member] \| Fair Value, Inputs, Level 2 [Member] \| Change In Plan Assets [Member]
Fair value of plan assets	911	1,626
Pension Plan [Member] \| Fair Value, Inputs, Level 3 [Member] \| Change In Plan Assets [Member]
Fair value of plan assets	0	0
Pension Plan [Member] \| Fair Value Measured at Net Asset Value Per Share [Member] \| Change In Plan Assets [Member]
Fair value of plan assets	0	15,164
Pension Plan [Member] \| Defined Benefit Plan, Equity Securities [Member]
Fair value of plan assets	36,240	24,947
Pension Plan [Member] \| Defined Benefit Plan, Equity Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	36,240	21,780
Pension Plan [Member] \| Defined Benefit Plan, Equity Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	0	0
Pension Plan [Member] \| Defined Benefit Plan, Equity Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair value of plan assets	0	0
Pension Plan [Member] \| Defined Benefit Plan, Equity Securities [Member] \| Fair Value Measured at Net Asset Value Per Share [Member]
Fair value of plan assets	0	3,167
Pension Plan [Member] \| Defined Benefit Plan, Debt Security [Member]
Fair value of plan assets	19,628	29,922
Pension Plan [Member] \| Defined Benefit Plan, Debt Security [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	19,628	17,925
Pension Plan [Member] \| Defined Benefit Plan, Debt Security [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	0	0
Pension Plan [Member] \| Defined Benefit Plan, Debt Security [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair value of plan assets	0	0
Pension Plan [Member] \| Defined Benefit Plan, Debt Security [Member] \| Fair Value Measured at Net Asset Value Per Share [Member]
Fair value of plan assets	0	11,997
Pension Plan [Member] \| Defined Benefit Plan, Cash and Cash Equivalents [Member]
Fair value of plan assets	911	1,626
Pension Plan [Member] \| Defined Benefit Plan, Cash and Cash Equivalents [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair value of plan assets	0	0
Pension Plan [Member] \| Defined Benefit Plan, Cash and Cash Equivalents [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	911	1,626
Pension Plan [Member] \| Defined Benefit Plan, Cash and Cash Equivalents [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair value of plan assets	0	0
Pension Plan [Member] \| Defined Benefit Plan, Cash and Cash Equivalents [Member] \| Fair Value Measured at Net Asset Value Per Share [Member]
Fair value of plan assets	$ 0	$ 0