Balance Sheet - Additional Information (Detail)	3 Months Ended	12 Months Ended
Apr. 30, 2019 USD ($) customer	Jan. 31, 2019 USD ($) customer
Balance Sheet [Line Items]
Contracts receivable	$ 2,600,000	$ 3,000,000
Number of customers due \| customer	2	3
Contracts receivable, noncurrent	$ 465,000
Contracts receivable, interest rate	3.10%	3.60%
Impairment of long-lived assets	$ 0
Minimum
Balance Sheet [Line Items]
Contracts receivable repayment term	4 months
Maximum
Balance Sheet [Line Items]
Contracts receivable repayment term	33 months

The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 958
-SubTopic 220
-Section 45
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2420-110228

Name:	us-gaap_ImpairmentOfLongLivedAssetsHeldForUse
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration