Note 9 - Fair Value of Assets and Liabilities - Fair Value Measurements, Recorded (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Total assets at fair value	$ 19,733	$ 18,772
Total liabilities recorded at fair value	2,341	3,457
Supplemental Executive Retirement Plan [Member]
Derivative asset	17,516	15,061
Metal Swaps [Member]
Derivative asset	2,130	3,055
Embedded customer derivative	2,217	3,457
Embedded Customer Derivatives [Member]
Derivative asset		402
Embedded customer derivative	87
Interest Rate Swap [Member]
Derivative asset		254
Forward Interest Rate Hedge [Member]
Embedded customer derivative	124
Fair Value, Inputs, Level 1 [Member]
Total assets at fair value	17,516	15,061
Total liabilities recorded at fair value	0	0
Fair Value, Inputs, Level 1 [Member] \| Supplemental Executive Retirement Plan [Member]
Derivative asset	17,516	15,061
Fair Value, Inputs, Level 1 [Member] \| Metal Swaps [Member]
Derivative asset	0	0
Embedded customer derivative	0	0
Fair Value, Inputs, Level 1 [Member] \| Embedded Customer Derivatives [Member]
Derivative asset		0
Embedded customer derivative	0
Fair Value, Inputs, Level 1 [Member] \| Interest Rate Swap [Member]
Derivative asset		0
Fair Value, Inputs, Level 1 [Member] \| Forward Interest Rate Hedge [Member]
Embedded customer derivative	0
Fair Value, Inputs, Level 2 [Member]
Total assets at fair value	2,217	3,711
Total liabilities recorded at fair value	2,341	3,457
Fair Value, Inputs, Level 2 [Member] \| Supplemental Executive Retirement Plan [Member]
Derivative asset	0	0
Fair Value, Inputs, Level 2 [Member] \| Metal Swaps [Member]
Derivative asset	2,130	3,055
Embedded customer derivative	2,217	3,457
Fair Value, Inputs, Level 2 [Member] \| Embedded Customer Derivatives [Member]
Derivative asset		402
Embedded customer derivative	87
Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swap [Member]
Derivative asset		254
Fair Value, Inputs, Level 2 [Member] \| Forward Interest Rate Hedge [Member]
Embedded customer derivative	124
Fair Value, Inputs, Level 3 [Member]
Total assets at fair value	0	0
Total liabilities recorded at fair value	0	0
Fair Value, Inputs, Level 3 [Member] \| Supplemental Executive Retirement Plan [Member]
Derivative asset	0	0
Fair Value, Inputs, Level 3 [Member] \| Metal Swaps [Member]
Derivative asset	0	0
Embedded customer derivative	0	0
Fair Value, Inputs, Level 3 [Member] \| Embedded Customer Derivatives [Member]
Derivative asset		0
Embedded customer derivative	0
Fair Value, Inputs, Level 3 [Member] \| Interest Rate Swap [Member]
Derivative asset		$ 0
Fair Value, Inputs, Level 3 [Member] \| Forward Interest Rate Hedge [Member]
Embedded customer derivative	$ 0