CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Statement [Abstract]
Consolidated revenue	$ 528.0	$ 516.4	$ 1,517.8	$ 1,516.6
Consolidated expenses:
Compensation and related expenses	253.5	220.8	747.6	676.5
Selling, general and administrative	100.5	97.0	290.8	278.1
Intangible amortization and impairments	6.3	7.3	96.0	21.8
Interest expense	33.2	34.7	101.8	98.1
Depreciation and other amortization	2.6	3.3	7.9	9.4
Other expenses (net)	13.1	11.6	34.7	31.5
Total consolidated expenses	409.2	374.7	1,278.8	1,115.4
Equity method income (net)	88.5	52.6	229.5	188.3
Affiliate transaction gains	127.6	0.0	127.6	0.0
Investment and other income	27.6	22.8	64.7	60.0
Income before income taxes	362.5	217.1	660.8	649.5
Income tax expense	71.6	31.3	134.7	130.0
Net income	290.9	185.8	526.1	519.5
Net income (non-controlling interests)	(78.5)	(62.2)	(157.1)	(170.0)
Net income (controlling interest)	$ 212.4	$ 123.6	$ 369.0	$ 349.5
Average shares outstanding (basic) (in shares)	28.4	30.1	28.7	31.4
Average shares outstanding (diluted) (in shares)	32.9	35.0	33.0	35.2
Earnings per share (basic) (in dollars per share)	$ 7.47	$ 4.11	$ 12.85	$ 11.11
Earnings per share (diluted) (in dollars per share)	$ 6.87	$ 3.78	$ 11.83	$ 10.25

Amortization and Impairments of Intangible Assets

No definition available.

Name:	amg_AmortizationandImpairmentsofIntangibleAssets
Namespace Prefix:	amg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The aggregate expense charged against earnings to allocate the cost of tangible assets to periods in which the assets are used and held and to allocate the cost of issuing debt to periods in which the debt is outstanding. As a noncash expense, this element is added back to net income when calculating cash provided by (used in) operations using the indirect method.

+ References

No definition available.