Revenue from Contracts with Customers - Schedule of Impact on Consolidated Balance Sheet of Adopting ASC 606 (Detail) - USD ($) $ in Thousands	Jul. 31, 2018	Feb. 01, 2018	Jan. 31, 2018
Assets
Unbilled receivables	$ 5,330	$ 3,238	$ 3,101
Prepaid expenses and other current assets	4,996	4,381	3,557
Liabilities
Deferred revenues	8,504	13,075
Stockholders' equity:
Accumulated loss	(160,852)	(146,301)	(148,620)
Under ASC 605 [Member] | ASU 2014-09 [Member]
Assets
Unbilled receivables	5,114		3,101
Prepaid expenses and other current assets	4,361		3,557
Liabilities
Deferred revenues	13,755		14,433
Stockholders' equity:
Accumulated loss	(166,954)		$ (148,620)
Adjustment [Member] | ASU 2014-09 [Member]
Assets
Unbilled receivables	216	137
Prepaid expenses and other current assets	635	824
Liabilities
Deferred revenues	(5,251)	(1,358)
Stockholders' equity:
Accumulated loss	$ 6,102	$ 2,319