Financial Instruments and Commodity Contracts - Narrative (Details) (USD $)	3 Months Ended						1 Months Ended	3 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2013 Interest Rate Contract [Member]	Oct. 31, 2012 Interest Rate Contract [Member]	Oct. 31, 2013 Variable Rate [Domain]	Oct. 31, 2009 Call Option [Member] Convertible Subordinated Debt [Member] Manufacturing Operations [Member]	Oct. 31, 2009 Call Option [Member] Convertible Subordinated Debt [Member] Manufacturing Operations [Member]	Oct. 31, 2013 Steel Forward Contracts [Member] Commodity Contract [Member]	Oct. 31, 2012 Steel Forward Contracts [Member] Commodity Contract [Member]	Oct. 31, 2013 Diesel Fuel Forward Contracts [Member] Commodity Contract [Member]	Oct. 31, 2012 Diesel Fuel Forward Contracts [Member] Commodity Contract [Member]
Derivative [Line Items]
Payments for Derivative Instrument, Investing Activities							$ 125,000,000	$ 125,000,000
Derivative, Amount of Hedged Item	0	0	0
Derivative, Collateral, Obligation to Return Cash	0	1,000,000
Derivative, Notional Amount				45,000,000	39,000,000	78,000,000			11,000,000	61,000,000	2,000,000	3,000,000
Exposure to credit risk	$ 5,000,000	$ 0