Share-based payment plans - Share appreciation rights (Details) - Cash-settled SARs	12 Months Ended
Dec. 31, 2017
2013 plan
Share-based payment plans
Vesting period	3 years
Vesting percentage	33.00%
Expiration period	5 years
2017 plan
Share-based payment plans
Vesting period	4 years
Vesting percentage	25.00%
Expiration period	10 years

Period which the right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

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Namespace Prefix:	maxr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration