Geographic Information Summary of Revenues by Geographic Area (Detail) $ in Thousands	3 Months Ended	9 Months Ended
Oct. 31, 2018 USD ($) market	Oct. 31, 2017 USD ($)	Oct. 31, 2018 USD ($) market	Oct. 31, 2017 USD ($)
Disaggregation of Revenue [Line Items]
Number of primary geographical markets \| market	2		2
Revenue	$ 743,189	$ 555,389	$ 2,033,552	$ 1,560,570
United States
Disaggregation of Revenue [Line Items]
Revenue	573,473	439,794	1,568,812	1,242,431
Other countries
Disaggregation of Revenue [Line Items]
Revenue	$ 169,716	$ 115,595	$ 464,740	$ 318,139

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration