CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Consolidated revenue	$ 471.1	$ 591.9	$ 978.3	$ 1,135.1
Consolidated expenses:
Compensation and related expenses	216.5	258.0	424.4	486.2
Selling, general and administrative	73.6	96.2	163.8	191.8
Intangible amortization and impairments	80.9	21.2	101.5	50.9
Interest expense	22.3	19.7	41.8	37.9
Depreciation and other amortization	5.0	5.3	10.1	10.6
Other expenses (net)	11.3	12.2	22.3	23.0
Total consolidated expenses	409.6	412.6	763.9	800.4
Equity method income (loss) (net)	17.4	29.4	(95.8)	(328.8)
Investment and other income (expense)	(12.1)	7.2	(9.7)	15.2
Income before income taxes	66.8	215.9	108.9	21.1
Income tax expense (benefit)	3.3	35.7	5.5	(26.1)
Net income	63.5	180.2	103.4	47.2
Net income (non-controlling interests)	(32.8)	(72.5)	(88.3)	(140.3)
Net income (loss) (controlling interest)	$ 30.7	$ 107.7	$ 15.1	$ (93.1)
Average shares outstanding (basic) (in shares)	47.2	51.0	47.5	51.5
Average shares outstanding (diluted) (in shares)	47.3	51.0	47.6	51.5
Earnings (loss) per share (basic) (in dollars per share)	$ 0.65	$ 2.11	$ 0.32	$ (1.81)
Earnings (loss) per share (diluted) (in dollars per share)	$ 0.65	$ 2.11	$ 0.32	$ (1.81)

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.