Note 4 - Financiang arrangements (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Line of Credit Facility, Maximum Borrowing Capacity	$ 350
Line of Credit Facility, Amount Outstanding	15.0
Debt, Weighted Average Interest Rate	0.70%
Unsecured Debt	200.0
Debt Instrument, Interest Rate Terms	The applicable interest rate on the Base Rate loans is the greater of the Federal Funds Rate plus 1/2 of 1% or the Prime Rate in effect on the day of the loan.The applicable interest rate on the Eurodollar Rate loans is based on LIBOR plus an applicable margin and other fees.
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	1.35%
Senior Notes	449.3	649.2
Term Loan Facility Outstanding [Member]
Unsecured Debt	200.0
Term Loan Facility Installment Payment [Member]
Debt Instrument, Periodic Payment, Principal	50
Term Loan Facility Remaining Payment [Member]
Debt Instrument, Periodic Payment, Principal	150
Senior Notes Matured [Member]
Senior Notes	200.0
Debt Instrument, Interest Rate, Stated Percentage	5.31%
Senior Notes First Issuance [Member]
Senior Notes	200.0
Debt Instrument, Interest Rate, Stated Percentage	6.08%
Required Installment Payment [Member]
Repayments of Unsecured Debt	50.0
Senior Notes Second Issuance [Member]
Senior Notes	$ 250.0
Debt Instrument, Interest Rate, Stated Percentage	3.375%

Interest rate stated in the contractual debt agreement.

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Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

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Reflects the calculation as of the balance sheet date of the average interest rate weighted by the amount of debt outstanding by type or by instrument at that time.

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Amount borrowed under the credit facility as of the balance sheet date.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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