Credit Facility (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Apr. 30, 2011
Credit Facility  
Line of credit facility, initiation date April 29, 2011
Line of credit facility, maximum borrowing capacity $ 1,250
Line of credit facility, term (years) 5
Credit facility financial covenants
Leverage ratio at balance sheet date 2.0
Fixed charge coverage ratio at balance sheet date 3.8
Asset coverage ratio at balance sheet date 17
Total standby and import letters of credit $ 197