Note 7 - Stock-based Compensation (Details) - Stock Options Activity (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Stock Options Activity [Abstract]
Outstanding, Number of options	627,550	[1],[2]	898,732	[1]	1,528,590	[1]	1,823,154
Outstanding, Weighted average exercise price	$ 36.41	[1],[2]	$ 36.55	[1]	$ 36.09	[1]	$ 35.61
Outstanding, Weighted average remaining life (in years)	2 years 73 days	[1],[2]	3 years	[1]
Outstanding, Aggregate intrinsic value (in millions)	$ 11	[1],[2]	$ 10	[1]
Exercised, Number of options	(267,182)		(617,358)		(234,844)
Exercised, Weighted average exercise price	$ 36.84		$ 35.37		$ 32.07
Exercised, Weighted average remaining life (in years)	1 year 255 days
Forfeited, Number of options	(4,000)		(12,500)		(59,720)
Forfeited, Weighted average exercise price	$ 39.71		$ 38.36		$ 37.34
Forfeited, Weighted average remaining life (in years)	2 years 255 days

[1] All options outstanding at December 31, 2014, 2013 and 2012 were exercisable.

[2] The range of exercise prices for the options outstanding at December 31, 2014 was $31.09 to $43.54.