Nature of Operations - Additional Information (Details)	12 Months Ended
Dec. 31, 2017	May 12, 2017
Disclosure Of Nature Of Operations [Line Items]
Ratio of pre-consolidated common shares to post-consolidated common share		10.00%
Ana Paula Property \| Mexico \| Minera Aurea
Disclosure Of Nature Of Operations [Line Items]
Proportion of ownership interest in property	100.00%

Ratio of pre-consolidated common shares to post-consolidated common share.

No definition available.

Name:	alo_RatioOfPreConsolidatedCommonSharesToPostConsolidatedCommonShare
Namespace Prefix:	alo_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant