Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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ACQUISITIONS - Intangible assets acquired (Details) - USD ($) $ in Millions	Dec. 31, 2020	Aug. 04, 2020	Jul. 01, 2020	Jun. 01, 2020	Feb. 03, 2020
Hanweck
Acquisitions
Finite-lived intangible assets acquired					$ 14.0
FT Options
Acquisitions
Finite-lived intangible assets acquired					6.3
Trade Alert
Acquisitions
Finite-lived intangible assets acquired				$ 2.0
EuroCCP
Acquisitions
Finite-lived intangible assets acquired			$ 32.3
MATCHNow
Acquisitions
Finite-lived intangible assets acquired		$ 36.7
BIDS Holdings
Acquisitions
Finite-lived intangible assets acquired	$ 156.4
Customer relationships \| Hanweck
Acquisitions
Finite-lived intangible assets acquired					$ 4.9
Useful Life (Years)					13 years
Customer relationships \| FT Options
Acquisitions
Finite-lived intangible assets acquired					$ 2.2
Useful Life (Years)					13 years
Customer relationships \| Trade Alert
Acquisitions
Finite-lived intangible assets acquired				$ 0.7
Useful Life (Years)				13 years
Customer relationships \| MATCHNow
Acquisitions
Finite-lived intangible assets acquired		$ 17.4
Useful Life (Years)		15 years
Customer relationships \| BIDS Holdings
Acquisitions
Finite-lived intangible assets acquired	$ 137.0
Useful Life (Years)	17 years
Technology \| Hanweck
Acquisitions
Finite-lived intangible assets acquired					$ 2.1
Useful Life (Years)					4 years
Technology \| FT Options
Acquisitions
Finite-lived intangible assets acquired					$ 0.9
Useful Life (Years)					4 years
Technology \| Trade Alert
Acquisitions
Finite-lived intangible assets acquired				$ 0.3
Useful Life (Years)				4 years
Technology \| EuroCCP
Acquisitions
Finite-lived intangible assets acquired			$ 3.6
Useful Life (Years)			6 years
Technology \| MATCHNow
Acquisitions
Finite-lived intangible assets acquired		$ 0.7
Useful Life (Years)		7 years
Technology \| BIDS Holdings
Acquisitions
Finite-lived intangible assets acquired	$ 17.8
Useful Life (Years)	11 years
Trademarks and tradenames \| Hanweck
Acquisitions
Finite-lived intangible assets acquired					$ 7.0
Useful Life (Years)					10 years
Trademarks and tradenames \| FT Options
Acquisitions
Finite-lived intangible assets acquired					$ 3.2
Useful Life (Years)					10 years
Trademarks and tradenames \| Trade Alert
Acquisitions
Finite-lived intangible assets acquired				$ 1.0
Useful Life (Years)				10 years
Trademarks and tradenames \| EuroCCP
Acquisitions
Finite-lived intangible assets acquired			$ 0.6
Useful Life (Years)			10 years
Trademarks and tradenames \| MATCHNow
Acquisitions
Finite-lived intangible assets acquired		$ 0.2
Useful Life (Years)		2 years
Trademarks and tradenames \| BIDS Holdings
Acquisitions
Finite-lived intangible assets acquired	$ 1.6
Useful Life (Years)	10 years
Trading registrations and licenses \| EuroCCP
Acquisitions
Indefinite-lived intangible assets acquired			$ 28.1
Trading registrations and licenses \| MATCHNow
Acquisitions
Indefinite-lived intangible assets acquired		$ 18.4