Note F - Stock-based Compensation - Activity for Non-vested Restricted Stock (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Non-vested, shares (in shares)	22,721	18,604	32,337
Non-vested, weighted average fair value at grant date (in dollars per share)	$ 96.82	$ 93.23	$ 87.84
Granted, shares (in shares)	9,238	7,310	4,138
Granted, weighted average fair value at grant date (in dollars per share)	$ 90.01	$ 89.84	$ 98.54
Vested, shares (in shares)	(2,981)	(3,193)	(17,871)
Vested, weighted average fair value at grant date (in dollars per share)	$ 88.23	$ 59.94	$ 84.71
Forfeited, shares (in shares)	(44)	0	0
Forfeited, weighted average fair value at grant date (in dollars per share)	$ 88.41
Non-vested, shares (in shares)	28,934	22,721	18,604
Non-vested, weighted average fair value at grant date (in dollars per share)	$ 95.54	$ 96.82	$ 93.23