Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Jul. 31, 2018	Jul. 31, 2017
Payables and Accruals [Abstract]
Trade accounts payable	$ 65,057	$ 20,626
Accounts payable to sellers	68,660	50,534
Buyer deposits and prepayments	62,443	50,603
Accrued compensation and benefits	37,218	31,173
Accrued insurance	4,376	5,263
Other accrued liabilities	33,190	50,216
Total accounts payable and accrued expenses	$ 270,944	$ 208,415