Note 9 - Non-pension Post-retirement Benefits - Benefit Obligation (Details) - Non-Pension Post-retirement Benefit Plans [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Projected benefit obligation	$ 46,966	$ 53,943
Service cost	444	605
Interest cost	1,872	1,860
Plan participants’ contributions	409	512
Actuarial (gain) loss	4,625	(5,411)
Exchange rate fluctuations	49	(96)
Benefits paid	(5,041)	(4,447)
Projected benefit obligation	49,324	46,966
Funded status and accrued benefit cost	49,324	46,966
UNITED STATES
Projected benefit obligation	45,899	52,648
Service cost	443	604
Interest cost	1,836	1,822
Plan participants’ contributions	409	512
Actuarial (gain) loss	4,666	(5,305)
Exchange rate fluctuations
Benefits paid	(4,990)	(4,382)
Projected benefit obligation	48,263	45,899
Funded status and accrued benefit cost	48,263	45,899
Foreign Plan [Member]
Projected benefit obligation	1,067	1,295
Service cost	1	1
Interest cost	36	38
Plan participants’ contributions
Actuarial (gain) loss	(41)	(106)
Exchange rate fluctuations	49	(96)
Benefits paid	(51)	(65)
Projected benefit obligation	1,061	1,067
Funded status and accrued benefit cost	$ 1,061	$ 1,067