Note 13 - Stock Compensation - Summary of the Status of the Stock Option Plan (Details) - $ / shares				12 Months Ended
	Oct. 01, 2018	Jan. 01, 2018	Mar. 03, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balance, vested (in shares)				7,000
Balance, weighted average exercise price per share (in dollars per share)				$ 27.99
Balance, non-vested shares (in shares)		35,000		40,000	35,000
Balance, weighted average exercise price per share, non-vested (in dollars per share)		$ 27.99		$ 28.71	$ 27.99
Balance (in shares)		35,000		47,000	35,000
Balance, weighted average exercise price (in dollars per share)		$ 27.99		$ 28.60	$ 27.99
Granted, non-vested shares (in shares)	5,000	7,000	35,000		12,000	35,000
Granted, weighted average exercise price per share, non-vested (in dollars per share)					$ 30.40
Granted, weighted average exercise price (in dollars per share)	$ 30.14	$ 30.58	$ 27.99		$ 30.40
Forfeited, non-vested shares (in shares)				(2,000)
Forfeited, weighted average exercise price per share, non-vested (in dollars per share)				$ (30.14)
Forfeited (in shares)				(2,000)
Forfeited, weighted average exercise price (in dollars per share)				$ 30.14
Exercised (in shares)
Exercised, weighted average exercise price (in dollars per share)
Vested, vested (in shares)				9,400	7,000
Vested, weighted average exercise price per share (in dollars per share)				$ 28.60	$ 27.99
Vested, non-vested shares (in shares)				(9,400)	(7,000)
Vested, weighted average exercise price per share, non-vested (in dollars per share)				$ 28.60	$ 27.99
Balance, vested (in shares)				16,400	7,000
Balance, weighted average exercise price per share (in dollars per share)				$ 28.34	$ 27.99
Balance, non-vested shares (in shares)				28,600	40,000	35,000
Balance, weighted average exercise price per share, non-vested (in dollars per share)				$ 28.65	$ 28.71	$ 27.99
Balance (in shares)				45,000	47,000	35,000
Balance, weighted average exercise price (in dollars per share)				$ 28.54	$ 28.60	$ 27.99
Options exercisable at year end, vested (in shares)
Options exercisable at year end (in shares)
Options exercisable at year end, weighted average exercise price (in dollars per share)
Remaining contractual life (years), vested (Year)				3 years 73 days	4 years
Remaining contractual life (years), non-vested shares (Year)				3 years 109 days	4 years 146 days
Remaining contractual life (years), outstanding shares (Year)				3 years 109 days	4 years 146 days
Options exercisable at year end, weighted average exercise price per share, vested (in dollars per share)