Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Operating Loss Carryforwards [Line Items]
Impairment charges	$ 0	$ 0	$ 46,867,000
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount		39,800,000
Unrecognized Tax Benefits	$ 18,362,000	15,294,000	21,133,000	$ 17,849,000
Foreign Net Operating Loss Carryforwards Expiration Dates	five years
State Net Operating Loss Carryforwards Expiration Dates	2022 to 2034
Foreign Tax Credit Carryforward Expiration Dates	2021 to 2027
State Research And Development Tax Credit Carryforward Expiration Dates	2018 to 2033
Valuation Allowance, Deferred Tax Asset, Change in Amount	$ 571,000	1,930,000
Unrecognized Tax Benefits, Interest on Income Taxes Expense	674,000	3,000	157,000
Unrecognized Tax Benefits, Income Tax Penalties Expense	0		66,000
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	2,239,000	1,530,000
Unrecognized Tax Benefits, Income Tax Penalties Accrued	2,948,000	3,000
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	1,748,000
Unrecognized Tax Benefits Recognized In Other Liabilities	11,725,000	9,304,000
Reduction Of Longterm Deferred Income Tax Assets Excluding Interest and Penalties	6,637,000	5,990,000
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	726,000
Undistributed Earnings of Foreign Subsidiaries	244,123,000
Cash Held Outside the U.S.	94,861
Cash and cash equivalents	133,944,000	$ 141,228,000	$ 114,492,000	$ 81,834,000
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	126,423,000
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration	99,077,000
Other Tax Carryforward, Gross Amount	27,022,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	35,875,000
Other Tax Carryforward, Gross Amount	11,028,000
Maximum recorded through earnings [Member]
Operating Loss Carryforwards [Line Items]
Unrecognized Tax Benefits, Income Tax Penalties Accrued	$ 1,748,000
United States, Federal [Member] | Low end of range [Member]
Operating Loss Carryforwards [Line Items]
Open Tax Year	2015
United States, Federal [Member] | High end of range [Member]
Operating Loss Carryforwards [Line Items]
Open Tax Year	2017
FRANCE | Low end of range [Member]
Operating Loss Carryforwards [Line Items]
Open Tax Year	2014
FRANCE | High end of range [Member]
Operating Loss Carryforwards [Line Items]
Open Tax Year	2017
GERMANY | Low end of range [Member]
Operating Loss Carryforwards [Line Items]
Open Tax Year	2009
GERMANY | High end of range [Member]
Operating Loss Carryforwards [Line Items]
Open Tax Year	2017
UNITED KINGDOM | Low end of range [Member]
Operating Loss Carryforwards [Line Items]
Open Tax Year	2016
UNITED KINGDOM | High end of range [Member]
Operating Loss Carryforwards [Line Items]
Open Tax Year	2017