Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017
Indefinite Lived Intangible Assets By Major Class [Line Items]
Cost	$ 9,977	$ 3,570
Accumulated Amortization	1,634	1,273
Net	$ 8,343	$ 2,297
Completed technologies
Indefinite Lived Intangible Assets By Major Class [Line Items]
Amortization Period	5 years 3 months 18 days	6 years
Cost	$ 7,326	$ 2,370
Accumulated Amortization	1,051	833
Net	$ 6,275	$ 1,537
Customer relationships
Indefinite Lived Intangible Assets By Major Class [Line Items]
Amortization Period	3 years 9 months 18 days	6 years
Cost	$ 2,268	$ 970
Accumulated Amortization	468	341
Net	$ 1,800	$ 629
Trade names
Indefinite Lived Intangible Assets By Major Class [Line Items]
Amortization Period	4 years 2 months 12 days	5 years
Cost	$ 383	$ 230
Accumulated Amortization	115	99
Net	$ 268	$ 131