Treasury Stock - Additional Information (Detail) - shares	Apr. 30, 2017	Jan. 31, 2017
Equity [Abstract]
Number of shares authorized to repurchase	0	0

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant