Fair Value Measurements - Hierarchy Levels (Details) - Recurring basis - USD ($) $ in Thousands	Apr. 30, 2018	Jul. 31, 2017
Assets:
Total assets	$ 103	$ 102
Liabilities:
Assumed contingent obligation		12
Total accrued expenses		12
Long-term debt	169,000	126,000
Contingent consideration	1,262	1,126
Total other long-term liabilities:	1,262	1,126
Total liabilities	170,262	127,138
Money markets
Assets:
Money markets	103	102
Level 1
Assets:
Total assets	103	102
Liabilities:
Assumed contingent obligation		0
Total accrued expenses		0
Long-term debt	0	0
Contingent consideration	0	0
Total other long-term liabilities:	0	0
Total liabilities	0	0
Level 1 | Money markets
Assets:
Money markets	103	102
Level 2
Assets:
Total assets	0	0
Liabilities:
Assumed contingent obligation		0
Total accrued expenses		0
Long-term debt	169,000	126,000
Contingent consideration	0	0
Total other long-term liabilities:	0	0
Total liabilities	169,000	126,000
Level 2 | Money markets
Assets:
Money markets	0	0
Level 3
Assets:
Total assets	0	0
Liabilities:
Assumed contingent obligation		12
Total accrued expenses		12
Long-term debt	0	0
Contingent consideration	1,262	1,126
Total other long-term liabilities:	1,262	1,126
Total liabilities	1,262	1,138
Level 3 | Money markets
Assets:
Money markets	$ 0	$ 0