FAIR VALUE MEASUREMENT - Fair value hierarchy for assets and liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Assets:
Digital assets - safeguarded assets	$ 24.0	$ 22.4
Total assets	52.3		$ 37.1
Liabilities:
Contingent consideration liabilities	47.5		70.5
Digital assets - safeguarded liabilities	24.0	$ 22.4
Total liabilities	1,956.7		1,397.8
Level 1
Assets:
Digital assets - safeguarded assets	24.0
Total assets	52.3		37.1
Liabilities:
Digital assets - safeguarded liabilities	24.0
Total liabilities	49.4		28.0
Level 2
Liabilities:
Total liabilities	1,859.8		1,299.3
Level 3
Liabilities:
Contingent consideration liabilities	47.5		70.5
Total liabilities	47.5		70.5
Recurring
Assets:
Digital assets - safeguarded assets	24.0
Total assets	51.4		37.1
Liabilities:
Contingent consideration liabilities	47.5		70.5
Digital assets - safeguarded liabilities	24.0
Total liabilities	71.5		70.5
Recurring | U.S. Treasury securities
Assets:
Total assets	0.5		9.1
Recurring | Canadian short-term investments
Assets:
Total assets	1.5
Recurring | Marketable securities | Mutual funds
Assets:
Total assets	15.9		18.4
Recurring | Marketable securities | Money market funds
Assets:
Total assets	9.5		9.6
Recurring | Level 1
Assets:
Digital assets - safeguarded assets	24.0
Total assets	51.4		37.1
Liabilities:
Digital assets - safeguarded liabilities	24.0
Total liabilities	24.0
Recurring | Level 1 | U.S. Treasury securities
Assets:
Total assets	0.5		9.1
Recurring | Level 1 | Canadian short-term investments
Assets:
Total assets	1.5
Recurring | Level 1 | Marketable securities | Mutual funds
Assets:
Total assets	15.9		18.4
Recurring | Level 1 | Marketable securities | Money market funds
Assets:
Total assets	9.5		9.6
Recurring | Level 3
Liabilities:
Contingent consideration liabilities	47.5		70.5
Total liabilities	$ 47.5		$ 70.5