Long-Term Debt (Narrative) (Details)	0 Months Ended
	Jan. 21, 2012 USD ($)	Jan. 21, 2012 JPY (¥)	Dec. 17, 2011 USD ($)	Jul. 31, 2012 USD ($)	Jan. 03, 2012	Jul. 31, 2011 USD ($)	Jul. 31, 2012 Fixed Interest Rate [Member] USD ($)
Trading Activity, Gains and Losses, Net [Line Items]
Annual maturities of long-term debt in 2013				$ 500,000
Annual maturities of long-term debt in 2014				101,400,000
Annual maturities of long-term debt in 2017				50,000,000
Annual maturities of long-term debt thereafter				50,000,000
Estimated fair value of long-term debt with fixed interest rates							223,500,000
Total				205,829,000		253,619,000	201,100,000
Senior unsecured notes, interest rate			4.85%		1.418%
Long-term debt, principal payment	$ 15,400,000	¥ 1,200,000,000	$ 30,000,000