Fair Value Measurements - Hierarchy Levels (Details) - Recurring basis - USD ($) $ in Thousands	Oct. 31, 2017	Jul. 31, 2017
Assets:
Total assets	$ 102	$ 102
Liabilities:
Total liabilities	168,000	127,138
Accrued expenses:
Liabilities:
Assumed contingent obligation	0	12
Contingent guaranteed obligation	0	0
Total accrued expenses	0	12
Long-term debt	168,000	126,000
Other long-term liabilities:
Liabilities:
Assumed contingent obligation	0	1,126
Contingent guaranteed obligation	0	0
Total other long-term liabilities:	0	1,126
Money markets | Cash and cash equivalents:
Assets:
Money markets	102	102
Level 1
Assets:
Total assets	102	102
Liabilities:
Total liabilities	0	0
Level 1 | Accrued expenses:
Liabilities:
Assumed contingent obligation	0	0
Contingent guaranteed obligation	0	0
Total accrued expenses	0	0
Long-term debt	0	0
Level 1 | Other long-term liabilities:
Liabilities:
Assumed contingent obligation	0	0
Contingent guaranteed obligation	0	0
Total other long-term liabilities:	0	0
Level 1 | Money markets | Cash and cash equivalents:
Assets:
Money markets	102	102
Level 2
Assets:
Total assets	0	0
Liabilities:
Total liabilities	168,000	126,000
Level 2 | Accrued expenses:
Liabilities:
Assumed contingent obligation	0	0
Contingent guaranteed obligation	0	0
Total accrued expenses	0	0
Long-term debt	168,000	126,000
Level 2 | Other long-term liabilities:
Liabilities:
Assumed contingent obligation	0	0
Contingent guaranteed obligation	0	0
Total other long-term liabilities:	0	0
Level 2 | Money markets | Cash and cash equivalents:
Assets:
Money markets	0	0
Level 3
Assets:
Total assets	0	0
Liabilities:
Total liabilities	0	1,138
Level 3 | Accrued expenses:
Liabilities:
Assumed contingent obligation	0	12
Contingent guaranteed obligation	0	0
Total accrued expenses	0	12
Long-term debt	0	0
Level 3 | Other long-term liabilities:
Liabilities:
Assumed contingent obligation	0	1,126
Contingent guaranteed obligation	0	0
Total other long-term liabilities:	0	1,126
Level 3 | Money markets | Cash and cash equivalents:
Assets:
Money markets	$ 0	$ 0