Pension and Other Postretirement Benefit Plans - Employee Benefit Trust Shares (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Note 13 - Pension and Other Postretirement Benefit Plans - Employee Benefit Trust (EBT) Shares (Details)
Shares owned by Employee Benefit Trust, beginning balance (in shares)	181,611	329,090
Shares purchased (in shares)	3,697	7,267
Shares released and allocated (in shares)	(145,447)	(154,746)
Shares owned by Employee Benefit Trust, ending balance (in shares)	39,861	181,611
Market value of unallocated shares	$ 663,287	$ 3,924,614