Long-Term Obligations - Additional Information (Details) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended			24 Months Ended	36 Months Ended						12 Months Ended	69 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Apr. 30, 2012	Apr. 30, 2014	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2013	Jul. 31, 2007	May 13, 2010 Senior Unsecured Notes [Member]	Jul. 31, 2014 Euro-denominated notes payable in 2017 at a fixed rate of 3.71% [Member] Rate	May 13, 2010 Euro-denominated notes payable in 2017 at a fixed rate of 3.71% [Member]	Jul. 31, 2014 Euro-denominated notes payable in 2020 at a fixed rate of 4.24% [Member] Rate	May 13, 2010 Euro-denominated notes payable in 2020 at a fixed rate of 4.24% [Member]	Jul. 31, 2014 Private Placement Debt [Member]	May 01, 2010 Private Placement Debt [Member]	Apr. 30, 2012	Jul. 31, 2014	Jul. 31, 2014	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014 CNY-Denominated Borrowings [Member] [Member]
Debt Instrument [Line Items]
Line of credit, current borrowing capacity																	$ 300,000,000	$ 300,000,000				$ 26,200,000
Line of Credit Borrowing Capacity, Amended																						24,200,000
Line of credit, expiration date						Feb. 01, 2017
Line of credit, maximum borrowing capacity																	450,000,000	450,000,000
Proceeds from borrowing on notes payable			63,000,000	220,000,000	0													63,000,000	220,000,000
Repayments of Notes Payable		(39,000,000)	60,000,000	181,000,000	0												21,000,000
Line of Credit Facility, Maximum Amount Outstanding During Period																				72,000,000
Notes Payable, Current			61,422,000	50,613,000		50,613,000														42,000,000	39,000,000		6,923,000	11,613,000	12,499,000
Line of credit, remaining borrowing capacity																	254,366,000	254,366,000				4,778,000
Line of Credit Facility, Maximum Remaining Borrowing Capacity																	404,366,000	404,366,000
Letters of credit outstanding			3,634,000	3,570,000		3,570,000
Notes Payable																					39,000,000	19,422,000	6,923,000		12,499,000
Debt face amount								75,000,000.0		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			$ 216,280,000	$ 276,132,000		$ 276,132,000
Ratio Of Debt To Ebitda Related To Debt Agreement													equal to 1.7 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 1.7 to 1.0
Interest Expense Coverage Ratio	not less than a 3.0 to 1.0 ratio		equal to 11.5 to 1.0