Note 7 - Share-Based Compensation (Detail) - Stock Options Valuation Assumptions	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Minimum [Member]
Expected dividend yield at date of grant	2.63%	2.00%	2.86%
Expected stock price volatility	29.10%	28.70%	28.40%
Risk-free interest rate	0.56%	1.70%	1.55%
Expected life of options (in years)	4 years	4 years	4 years
Maximum [Member]
Expected dividend yield at date of grant	3.98%	2.55%	3.09%
Expected stock price volatility	31.70%	32.00%	31.20%
Risk-free interest rate	1.15%	2.14%	2.56%
Expected life of options (in years)	6 years	6 years	6 years