XML 91 R79.htm IDEA: XBRL DOCUMENT v3.23.3

Earnings Per Share - Additional Information (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended		3 Months Ended	9 Months Ended
	Jun. 30, 2023 $ / shares shares	Dec. 31, 2022 USD ($) shares	Sep. 30, 2023 $ / shares shares	Sep. 30, 2023 $ / shares shares
Earnings Per Share [Abstract]
Number or shares repurchased during period (in shares)	1.5		1.2	2.0
Average price of shares repurchased during period (in dollars per share) | $ / shares	$ 147.29		$ 137.34	$ 132.90
Accelerated share repurchase, upfront payment | $		$ 225.0
Accelerated share repurchase, stock delivered (in shares)	0.4	1.1
Percentage of shares delivered		0.80

X

- Definition

Accelerated Share Repurchase, Percentage Of Shares Received

+ References

No definition available.

+ Details

Name:	amg_AcceleratedShareRepurchasePercentageOfSharesReceived
Namespace Prefix:	amg_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Accelerated Share Repurchase, Stock Repurchased During Period, Shares

+ References

No definition available.

+ Details

Name:	amg_AcceleratedShareRepurchaseStockRepurchasedDuringPeriodShares
Namespace Prefix:	amg_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Accelerated Share Repurchase, Upfront Payment

+ References

No definition available.

+ Details

Name:	amg_AcceleratedShareRepurchaseUpfrontPayment
Namespace Prefix:	amg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	us-gaap_EarningsPerShareAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Total cost of shares repurchased divided by the total number of shares repurchased.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481549/505-30-45-1

+ Details

Name:	us-gaap_TreasuryStockAcquiredAverageCostPerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of shares that have been repurchased during the period and are being held in treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-SubTopic 10
-Topic 505
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-2

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_TreasuryStockSharesAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration