Note 5 - Benefit Plans - Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Balance outstanding (in dollars per share) | $ / shares	$ 20.15
Granted (in dollars per share) | $ / shares
Exercised (in dollars per share) | $ / shares
Forfeited (in dollars per share) | $ / shares	29.48
Balance outstanding (in dollars per share) | $ / shares	15.75
Options exercisable as of September 30, 2017 (in dollars per share) | $ / shares	$ 15.75
Incentive Stock Options [Member]
Balance outstanding (in shares)	60,000
Granted (in shares)
Exercised (in shares)
Forfeited (in shares)	(11,000)
Balance outstanding (in shares)	49,000
Options exercisable as of September 30, 2017 (in shares)	49,000
Non-Incentive Stock Options [Member]
Balance outstanding (in shares)	52,500
Granted (in shares)
Exercised (in shares)
Forfeited (in shares)	(25,000)
Balance outstanding (in shares)	27,500
Options exercisable as of September 30, 2017 (in shares)	27,500