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Fair Value Measurements - Financial Assets Measured on Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Catastrophe Bonds, Fair Value Disclosure	$ 2.4	$ 5.1	$ 5.3
Derivatives at fair value	17.2	56.2	12.9
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	6,245.6	6,100.9	6,512.6
Recurring | Derivatives at fair value | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives at fair value	17.2	56.2	12.9
Recurring | Liabilities under derivative contracts | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities under derivative contracts, fair value	(13.4)	(3.2)	(13.3)
Recurring | Liabilities under derivative contracts | Loss Portfolio Transfer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities under derivative contracts, fair value	(23.4)	(31.7)
Recurring | Total fixed income securities — Available for sale | Non-agency commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	5.7	5.6
Recurring | Fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	3,908.2	3,788.6	4,881.6
Recurring | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	169.3	52.0	10.1
Recurring | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	1,478.5	1,475.5	1,157.5
Privately-held Investments, at fair value	482.4	533.0	307.1
Catastrophe Bonds, Fair Value Disclosure	2.4	2.9	3.4
Recurring | Short-term investments trading at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	11.0	6.3	2.0
Recurring | Real estate fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	213.4	221.3	151.3
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	1,632.5	1,428.7	1,384.5
Recurring | Level 1 | Derivatives at fair value | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives at fair value		0.0	0.0
Recurring | Level 1 | Liabilities under derivative contracts | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities under derivative contracts, fair value	0.0	0.0	0.0
Recurring | Level 1 | Liabilities under derivative contracts | Loss Portfolio Transfer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities under derivative contracts, fair value	0.0	0.0
Recurring | Level 1 | Total fixed income securities — Available for sale | Non-agency commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0
Recurring | Level 1 | Fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	1,206.5	1,098.3	1,248.7
Recurring | Level 1 | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	169.2	51.9	6.5
Recurring | Level 1 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	247.7	272.2	128.2
Privately-held Investments, at fair value	0.0	0.0	0.0
Catastrophe Bonds, Fair Value Disclosure	0.0	0.0	0.0
Recurring | Level 1 | Short-term investments trading at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	9.1	6.3	1.1
Recurring | Level 1 | Real estate fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	3,940.7	3,949.6	4,669.7
Recurring | Level 2 | Derivatives at fair value | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives at fair value	17.2	56.2	12.9
Recurring | Level 2 | Liabilities under derivative contracts | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities under derivative contracts, fair value	(13.4)	(3.2)	(13.3)
Recurring | Level 2 | Liabilities under derivative contracts | Loss Portfolio Transfer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities under derivative contracts, fair value	0.0	0.0
Recurring | Level 2 | Total fixed income securities — Available for sale | Non-agency commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	5.7	5.6
Recurring | Level 2 | Fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	2,701.7	2,690.3	3,632.9
Recurring | Level 2 | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.1	0.1	3.6
Recurring | Level 2 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	1,230.8	1,203.3	1,029.3
Privately-held Investments, at fair value	0.0	0.0	0.0
Catastrophe Bonds, Fair Value Disclosure	2.4	2.9	3.4
Recurring | Level 2 | Short-term investments trading at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	1.9	0.0	0.9
Recurring | Level 2 | Real estate fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	459.0	501.3	307.1
Recurring | Level 3 | Derivatives at fair value | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives at fair value		0.0	0.0
Recurring | Level 3 | Liabilities under derivative contracts | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities under derivative contracts, fair value	0.0	0.0	0.0
Recurring | Level 3 | Liabilities under derivative contracts | Loss Portfolio Transfer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities under derivative contracts, fair value	(23.4)	(31.7)
Recurring | Level 3 | Total fixed income securities — Available for sale | Non-agency commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0
Recurring | Level 3 | Fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Recurring | Level 3 | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Recurring | Level 3 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Privately-held Investments, at fair value	482.4	533.0	307.1
Catastrophe Bonds, Fair Value Disclosure	0.0	0.0	0.0
Recurring | Level 3 | Short-term investments trading at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Recurring | Level 3 | Real estate fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
U.S. government | Recurring | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	1,013.8	953.0	1,084.3
U.S. government | Recurring | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	235.0	261.6	116.3
U.S. government | Recurring | Level 1 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	1,013.8	953.0	1,084.3
U.S. government | Recurring | Level 1 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	235.0	261.6	116.3
U.S. government | Recurring | Level 2 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
U.S. government | Recurring | Level 2 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
U.S. government | Recurring | Level 3 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
U.S. government | Recurring | Level 3 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
U.S. agency | Recurring | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	8.2	8.8	21.5
U.S. agency | Recurring | Level 1 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
U.S. agency | Recurring | Level 2 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	8.2	8.8	21.5
U.S. agency | Recurring | Level 3 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Municipal | Recurring | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	149.5	149.5	82.6
Municipal | Recurring | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	3.1	3.6	4.0
Municipal | Recurring | Level 1 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Municipal | Recurring | Level 1 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Municipal | Recurring | Level 2 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	149.5	149.5	82.6
Municipal | Recurring | Level 2 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	3.1	3.6	4.0
Municipal | Recurring | Level 3 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Municipal | Recurring | Level 3 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Corporate | Recurring | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	1,875.9	1,845.0	2,208.3
Corporate | Recurring | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	165.4	162.1	96.8
Corporate | Recurring | Level 1 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Corporate | Recurring | Level 1 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Corporate | Recurring | Level 2 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	1,875.9	1,845.0	2,208.3
Corporate | Recurring | Level 2 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	165.4	162.1	96.8
Corporate | Recurring | Level 3 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Corporate | Recurring | Level 3 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Non-U.S. government-backed corporate | Recurring | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	110.9	110.4	136.8
Non-U.S. government-backed corporate | Recurring | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	9.6	11.6	13.1
Non-U.S. government-backed corporate | Recurring | Level 1 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Non-U.S. government-backed corporate | Recurring | Level 1 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Non-U.S. government-backed corporate | Recurring | Level 2 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	110.9	110.4	136.8
Non-U.S. government-backed corporate | Recurring | Level 2 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	9.6	11.6	13.1
Non-U.S. government-backed corporate | Recurring | Level 3 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Non-U.S. government-backed corporate | Recurring | Level 3 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Non-U.S government | Recurring | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	269.2	213.6	250.7
Non-U.S government | Recurring | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	34.1	30.4	34.5
Non-U.S government | Recurring | Level 1 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	192.7	145.3	164.4
Non-U.S government | Recurring | Level 1 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	12.7	10.6	11.9
Non-U.S government | Recurring | Level 2 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	76.5	68.3	86.3
Non-U.S government | Recurring | Level 2 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	21.4	19.8	22.6
Non-U.S government | Recurring | Level 3 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Non-U.S government | Recurring | Level 3 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Asset-backed | Recurring | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		0.0	0.5
Asset-backed | Recurring | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	924.6	896.5	785.7
Asset-backed | Recurring | Level 1 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		0.0	0.0
Asset-backed | Recurring | Level 1 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Asset-backed | Recurring | Level 2 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		0.0	0.5
Asset-backed | Recurring | Level 2 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	924.6	896.5	785.7
Asset-backed | Recurring | Level 3 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		0.0	0.0
Asset-backed | Recurring | Level 3 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Non-agency commercial mortgage-backed securities | Recurring | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		5.6	6.9
Non-agency commercial mortgage-backed securities | Recurring | Level 1 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		0.0	0.0
Non-agency commercial mortgage-backed securities | Recurring | Level 2 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		5.6	6.9
Non-agency commercial mortgage-backed securities | Recurring | Level 3 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		0.0	0.0
Agency mortgage-backed | Recurring | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	475.0	502.7	1,090.0
Agency mortgage-backed | Recurring | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	20.1	21.4	30.2
Agency mortgage-backed | Recurring | Level 1 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Agency mortgage-backed | Recurring | Level 1 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Agency mortgage-backed | Recurring | Level 2 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	475.0	502.7	1,090.0
Agency mortgage-backed | Recurring | Level 2 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	20.1	21.4	30.2
Agency mortgage-backed | Recurring | Level 3 | Total fixed income securities — Available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
Agency mortgage-backed | Recurring | Level 3 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
High yield loans | Recurring | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	86.6	88.3	76.9
High yield loans | Recurring | Level 1 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	0.0	0.0	0.0
High yield loans | Recurring | Level 2 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	86.6	88.3	76.9
High yield loans | Recurring | Level 3 | Held for trading financial assets, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	$ 0.0	$ 0.0	$ 0.0

X

- Definition

Catastrophe Bonds, Fair Value Disclosure

+ References

No definition available.

+ Details

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Namespace Prefix:	ahl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Privately-held Investments, at fair value

+ References

No definition available.

+ Details

Name:	ahl_PrivatelyheldInvestmentsatfairvalue
Namespace Prefix:	ahl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
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