Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Aug. 31, 2017	Oct. 31, 2017	Jul. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses and other current assets		$ 729	$ 164
Long-term Purchase Commitment [Line Items]
Payments for Prepaid Research and Development Supplies		100
Cost to purchase research and development supplies		100
Research and Development Arrangement
Long-term Purchase Commitment [Line Items]
Payments to acquire in-process research and development	$ 418	$ 418