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Investment Securities - Fair Value of Hedge Funds and Private Equity Funds (Details) $ in Millions	Mar. 31, 2021 USD ($) fund	Dec. 31, 2020 USD ($)
Hedge and private equity funds included in other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 133.5	$ 121.2
Unfunded Commitments	$ 52.3	45.7
Hedge funds
Debt and Equity Securities, FV-NI [Line Items]
Number of investments | fund	1
Private equity funds
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 121.5	121.2
Unfunded Commitments	52.3	45.7
Private equity funds | Aerospace/Defense/Government
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	73.0	69.1
Unfunded Commitments	14.0	15.3
Private equity funds | Manufacturing/Industrial
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	1.3	28.6
Unfunded Commitments	0.0	0.0
Private equity funds | Financial services
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	43.2	23.5
Unfunded Commitments	35.3	30.4
Private equity funds | Real Estate
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	4.0	0.0
Unfunded Commitments	3.0	0.0
Hedge funds
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	12.0	0.0
Unfunded Commitments	0.0	0.0
Hedge funds | European small/mid cap
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	12.0	0.0
Unfunded Commitments	$ 0.0	$ 0.0

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- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258

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