CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Consolidated revenue	$ 2,027.5	$ 2,239.6	$ 2,378.4
Consolidated expenses:
Compensation and related expenses	883.7	943.0	987.2
Selling, general and administrative	321.4	376.8	417.7
Intangible amortization and impairments	140.5	144.5	114.8
Interest expense	92.3	76.2	80.6
Depreciation and other amortization	19.1	21.3	22.0
Other expenses (net)	52.8	57.0	69.7
Total consolidated expenses	1,509.8	1,618.8	1,692.0
Equity method loss (net)	(43.4)	(338.0)	(0.2)
Investment and other income	34.1	25.2	27.4
Income before income taxes	508.4	308.0	713.6
Income tax expense	81.4	2.9	181.3
Net income	427.0	305.1	532.3
Net income (non-controlling interests)	(224.8)	(289.4)	(288.7)
Net income (controlling interest)	$ 202.2	$ 15.7	$ 243.6
Average shares outstanding (basic) (in shares)	46.5	50.5	53.6
Average shares outstanding (diluted) (in shares)	46.7	50.6	53.8
Earnings per share (basic) (in dollars per share)	$ 4.34	$ 0.31	$ 4.55
Earnings per share (diluted) (in dollars per share)	$ 4.33	$ 0.31	$ 4.52

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.