Note 4 - Common Stock - Changes in Common Stock Issued and Outstanding (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Balance, shares issued (in shares)	184,735	184,735
Balance, treasury stock (in shares)	26,277	26,063
Balance, shares outstanding (in shares)	158,458	158,672
Purchase of stock (in shares)	554	214
Purchase of stock (in shares)	(554)	(214)
Balance, shares issued (in shares)	184,735	184,735
Balance, treasury stock (in shares)	26,831	26,277
Balance, shares outstanding (in shares)	157,904	158,458
Balance, treasury stock (in shares)	26,277	26,063
Balance, shares outstanding (in shares)	158,458	158,672