Note 6 - Share-based Compensation - Summary of Significant Assumptions for Share-based Compensation Awards (Details) - $ / shares		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term		5 years
Stock Appreciation Rights (SARs) [Member]
Exercise price (in dollars per share)		$ 16.97	$ 16.35
Market price (in dollars per share)		$ 16.97	$ 16.35
Risk free interest rate	[1]	1.90%	1.30%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	[2]	5 years
Expected volatility	[3]	36.60%	36.50%
Exoected dividend yield	[4]	2.10%	2.00%
Employee Stock Option [Member]
Exercise price (in dollars per share)		$ 16.97	$ 16.35
Market price (in dollars per share)		$ 16.97	$ 16.35
Risk free interest rate	[1]	1.90%	1.30%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	[2]	5 years
Expected volatility	[3]	36.60%	36.50%
Exoected dividend yield	[4]	2.10%	2.00%

[1] The risk-free interest rate is based on the yield of a U.S. treasury bond with a similar maturity as the expected life of the awards.

[2] The expected life in years for awards granted was based on the historical exercise patterns experienced by the Company when the award is made.

[3] The determination of expected stock price volatility for awards granted in each of the three-month periods ending March 31, 2017 and 2016 was based on historical prices of Superior's common stock over a period commensurate with the expected life.

[4] The dividend yield assumption is based on the history and expectation of the Company's dividend payouts.