Schedule of Share-Based Compensation Expense Included in Selling, General and Administrative Expenses in Condensed Consolidated Statements of Income (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Oct. 31, 2017	Oct. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reversal of share-based compensation expense	$ 6,509	$ 6,509
Performance Stock Units (PSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, granted	476,611	476,611

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration