Note 10 - Credit Facilities and Indebtedness (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended
	Apr. 23, 2013	Mar. 31, 2013
Line of Credit Facility, Maximum Borrowing Capacity		$ 750.0
Potential Increase In Line Of Credit Facility	250.0
Net Funded Debt Base Amount	150.0
Debt Instrument, Basis Spread on Variable Rate (in Basis Points)	1.00%
Debt Issuance Cost	3.3
Deferred Offering Costs	8.2
Domestic Credit Facility [Member]
Line of Credit Facility, Revolving Credit		120.0
Line of Credit Facility, Maximum Borrowing Capacity		750.0
Letters of Credit [Member]
Line of Credit Facility, Remaining Borrowing Capacity		606.8
Performance Bonds [Member]
Line Of Credit Facility Reserved For Letters Of Credit		23.2
Interest Coverage Ratio [Member]
Line of Credit Facility, Covenant Terms	3.0
Net Funded Debt Leverage Ratio [Member]
Line of Credit Facility, Covenant Terms	3.5
Letters of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity	50.0
Swingling Borrowing [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 50.0
Facility Fee [Member]
Debt Instrument, Basis Spread on Variable Rate (in Basis Points)	0.175%