CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Consolidated revenue	$ 2,239.6	$ 2,378.4	$ 2,305.0
Consolidated expenses:
Compensation and related expenses	943.0	987.2	979.0
Selling, general and administrative	376.8	417.7	373.1
Intangible amortization and impairments	144.5	114.8	86.4
Interest expense	76.2	80.6	87.8
Depreciation and other amortization	21.3	22.0	20.3
Other expenses (net)	57.0	69.7	58.0
Total consolidated expenses	1,618.8	1,692.0	1,604.6
Equity method income (loss) (net)	(338.0)	(0.2)	302.2
Investment and other income	25.2	27.4	64.5
Income before income taxes	308.0	713.6	1,067.1
Income tax expense	2.9	181.3	58.4
Net income	305.1	532.3	1,008.7
Net income (non-controlling interests)	(289.4)	(288.7)	(319.2)
Net income (controlling interest)	$ 15.7	$ 243.6	$ 689.5
Average shares outstanding (basic) (in shares)	50.5	53.6	56.0
Average shares outstanding (diluted) (in shares)	50.6	53.8	58.6
Earnings per share (basic) (in dollars per share)	$ 0.31	$ 4.55	$ 12.30
Earnings per share (diluted) (in dollars per share)	$ 0.31	$ 4.52	$ 12.03

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.