Note 7 - Stock-based Awards - Summary of Shares Granted Under the 2006 Incentive Plan (Details) - $ / shares			12 Months Ended
		May 04, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross		121,000	121,000
Fair value per share (in dollars per share)			$ 18.87
May 4, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			121,000
Fair value per share (in dollars per share)	[1]		$ 4.46
May 4, 2017 [Member] | Stock Unit Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			13,000
Fair value per share (in dollars per share)	[1]		$ 18.87
May 12, 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			121,000
Fair value per share (in dollars per share)	[1]		$ 2.34
May 12, 2016 [Member] | Stock Unit Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			17,000
Fair value per share (in dollars per share)	[1]		$ 13.82
September 15, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			47,000
Fair value per share (in dollars per share)	[1]		$ 1.91
September 15, 2015 [Member] | Stock Unit Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			1,000
Fair value per share (in dollars per share)	[1]		$ 10.21
April 29, 2015 [Member] | Stock Unit Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			44,000
Fair value per share (in dollars per share)	[1]		$ 16.10

[1] The fair value for the SUA's is the closing price of the Company's stock on that date. The fair value for options represents the fair value calculated using the Black-Scholes model. Options have contractual lives of 10 years and the fair value calculated using a Black-Scholes model. The options granted on September 15, 2015 have a fair value of $1.91 per share based on the $10.21 grant date and exercise prices and assuming a 6.5 year estimated term, 36% volatility, 2.2% interest rate and a 6.0% dividend yield rate. The options granted on May 12, 2016 have a fair value of $2.34 per share based on the $13.82 grant date and exercise prices and assuming a 6.25 year estimated term, 33% volatility, 1.75% interest rate and a 5.6% dividend yield rate. The options granted on May 4, 2017 have a fair value of $4.46 per share based on the $18.87 grant date and exercise prices and assuming a 6.25 year estimated term, 37% volatility, 2.75% interest rate and a 4.7% dividend yield rate.