Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies (Details)

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Commitments and Contingencies (Details) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Feb. 29, 2012
JP Morgan Chase Bank, N.A. [Member]
 
Lines of credit  
Amount available $ 350
Expiration date February 2013
Bank of America, N.A. [Member]
 
Lines of credit  
Amount available 250
Expiration date February 2013
PNC Bank, National Association [Member]
 
Lines of credit  
Amount available 150
Expiration date February 2013
Wells Fargo Bank, National Association [Member]
 
Lines of credit  
Amount available $ 150
Expiration date February 2013