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Investment Securities - Investments In Private Equity Funds Subject to Lock-Up Periods (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) fund	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Investment securities
Number of investments | fund	14
Fair value investments	$ 2,796.2	$ 2,746.0	$ 2,328.7
Private equity funds
Investment securities
Trading security, fair value	$ 121.2
Insurance-linked securities funds
Investment securities
Number of investments | fund	4
Fair value investments	$ 51.4
1 – 3 years | Private equity funds
Investment securities
Trading security, fair value	8.0
3 – 5 years | Private equity funds
Investment securities
Trading security, fair value	40.7
5 – 10 years | Private equity funds
Investment securities
Trading security, fair value	64.7
>10 years | Private equity funds
Investment securities
Trading security, fair value	$ 7.8
Minimum
Investment securities
Redemptions and advanced redemption notice period	30 days
Maximum
Investment securities
Redemptions and advanced redemption notice period	90 days

X

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Trading Security, Fair Value

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