Shareholders' equity - Share Repurchase (Details) $ in Millions	Oct. 31, 2020 USD ($)
Equity [Abstract]
Remaining authorized repurchase amount	$ 165.6

Amount remaining of a stock repurchase plan authorized.

No definition available.

Name:	us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant