Commitments and contingencies - Schedule of Contractual Obligations (Details) $ in Millions	Jun. 30, 2024 USD ($)
Other Commitments [Line Items]
Total	$ 991.5
Less than 1 year	143.6
1 - 3 years	197.7
3 - 5 years	487.9
More than 5 years	162.4
Accounts payable and accrued liabilities
Other Commitments [Line Items]
Total	136.0
Less than 1 year	129.7
1 - 3 years	6.3
3 - 5 years	0.0
More than 5 years	0.0
Lease liabilities
Other Commitments [Line Items]
Total	238.0
Less than 1 year	13.7
1 - 3 years	26.4
3 - 5 years	36.9
More than 5 years	161.1
Restoration provisions
Other Commitments [Line Items]
Total	1.6
Less than 1 year	0.2
1 - 3 years	0.1
3 - 5 years	0.0
More than 5 years	1.3
Convertible debt principal
Other Commitments [Line Items]
Total	375.0
Less than 1 year	0.0
1 - 3 years	100.0
3 - 5 years	275.0
More than 5 years	0.0
Convertible debt interest
Other Commitments [Line Items]
Total	240.9
Less than 1 year	0.0
1 - 3 years	64.9
3 - 5 years	176.0
More than 5 years	$ 0.0