Note F - Stock-based Compensation - Activity for Non-vested Restricted Stock (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Vested, shares (in shares)	(3.1)
Restricted Stock [Member]
Non-vested, shares (in shares)	32,336	28,934	22,721
Non-vested, weighted average fair value at grant date (in dollars per share)	$ 89.49	$ 95.54	$ 96.82
Granted, shares (in shares)	1,487	7,271	9,238
Granted, weighted average fair value at grant date (in dollars per share)	$ 77.03	$ 70.72	$ 90.01
Vested, shares (in shares)	(4,109)	(3,482)	(2,981)
Vested, weighted average fair value at grant date (in dollars per share)	$ 68.46	$ 100.05	$ 88.23
Forfeited, shares (in shares)	(43)	(387)	(44)
Forfeited, weighted average fair value at grant date (in dollars per share)	$ 93.29	$ 93.91	$ 88.41
Non-vested, shares (in shares)	29,671	32,336	28,934
Non-vested, weighted average fair value at grant date (in dollars per share)	$ 88.37	$ 89.49	$ 95.54