Long-Term Obligations - Additional Information (Details)	3 Months Ended	12 Months Ended			24 Months Ended	36 Months Ended												12 Months Ended	69 Months Ended	3 Months Ended	12 Months Ended		12 Months Ended
	Apr. 30, 2012	Jul. 31, 2013 USD ($)	Jul. 31, 2012 USD ($)	Jul. 31, 2011 USD ($)	Jul. 31, 2013 USD ($)	Jul. 31, 2007 USD ($)	Jul. 31, 2012 EUR (€)	Jul. 31, 2013 USD-Denominated Borrowing Credit Revolver [Member] USD ($)	Jul. 31, 2013 Senior Unsecured Notes [Member] EUR (€)	May 13, 2010 Senior Unsecured Notes [Member] USD ($)	May 13, 2010 Senior Unsecured Notes [Member] EUR (€)	Jul. 31, 2013 Euro-denominated notes payable in 2017 at a fixed rate of 3.71% [Member] USD ($)	Jul. 31, 2012 Euro-denominated notes payable in 2017 at a fixed rate of 3.71% [Member] USD ($)	May 13, 2010 Euro-denominated notes payable in 2017 at a fixed rate of 3.71% [Member] USD ($)	Jul. 31, 2013 Euro-denominated notes payable in 2020 at a fixed rate of 4.24% [Member] USD ($)	Jul. 31, 2012 Euro-denominated notes payable in 2020 at a fixed rate of 4.24% [Member] USD ($)	May 13, 2010 Euro-denominated notes payable in 2020 at a fixed rate of 4.24% [Member] USD ($)	Jul. 31, 2013 Private Placement Debt [Member]	May 01, 2010 Private Placement Debt [Member]	Apr. 30, 2012 USD-Denominated Borrowing Credit Revolver [Member]	Jul. 31, 2013 USD-Denominated Borrowing Credit Revolver [Member]	Jul. 31, 2013 USD-denominated credit facility China [Member] USD ($)	Jul. 31, 2013 USD-Denominated Borrowing Credit Revolver [Member] USD ($)	Jul. 31, 2013 USD-denominated credit facility China [Member] USD ($)
Debt Instrument [Line Items]
Line of credit, current borrowing capacity																						$ 26,200,000	$ 300,000,000
Line of credit, expiration date					Feb. 01, 2017
Line of credit, maximum borrowing capacity																							450,000,000
Proceeds from borrowing on notes payable		220,000,000	0	0																			220,000,000
Repayment of borrowing on notes payable		181,000,000	0	0
Notes Payable, Current		50,613,000	0		50,613,000			39,000,000
Line of credit, remaining borrowing capacity																							261,000,000	14,587,000
Excess Available Under Maximum Capacity		411,000,000			411,000,000
Letters of credit outstanding		3,570,000	3,762,000		3,570,000
Notes Payable																								11,613,000
Debt face amount							4,581,000		75,000,000.0	75,000,000.0	75,000,000			30,000,000.0			45,000,000.0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate												3.71%			4.24%
Debt Instrument Aggregate Face Amount During Period						500,000,000
Debt Instrument, Interest Rate Terms						from 5.14%to 5.33%
Repayments of Long-term Debt		61,300,000
Long-term debt, fair value		276,000,000	339,000,000		276,000,000
Long-term debt, carrying value		$ 262,414,000	$ 316,208,000		$ 262,414,000							$ 39,900,000	$ 36,912,000		$ 59,850,000	$ 55,368,000
Ratio Of Debt To Ebitda Related To Debt Agreement																		equal to 1.6 to 1.0	not more than a 3.5 to 1.0 ratio	not more than a 3.25 to 1.0 ratio	equal to 1.6 to 1.0
Interest Expense Coverage Ratio	not less than a 3.0 to 1.0 ratio	equal to 9.2 to 1.0