Note 4 - Long-Term And Fair Value Disclosure (Details) (USD $)	1 Months Ended
	Jun. 17, 2013	Jan. 31, 2014	Apr. 30, 2013	Dec. 17, 2013 Subsequent Event [Member] Series B 3.75% Notes [Member]	Dec. 17, 2013 Subsequent Event [Member] Senior Notes [Member]
Note 4 - Long-Term And Fair Value Disclosure (Details) [Line Items]
Long-term Debt, Fair Value		$ 849,000,000	$ 721,000,000
Line of Credit Facility, Maximum Borrowing Capacity		100,000,000
Line of Credit Facility, Amount Outstanding		0	59,100,000
Debt, Weighted Average Interest Rate		0.95%
Senior Notes				50,000,000
Debt Instrument, Interest Rate, Stated Percentage					3.75%
Line of Credit Facility, Decrease, Forgiveness	$ 25,000,000