Changes in the redemption value of Affiliate Equity and other transactions with Affiliate partners.

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Stock issued in connection with a purchase of a new Affiliate and the increase in non-controlling interests from new Affiliate investments.

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Amount of increase (decrease) in additional paid in capital (APIC) resulting from recognition of deferred taxes for convertible debt with a beneficial conversion feature.

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Amount of other increase (decrease) in additional paid in capital (APIC).

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This element represents the amount of recognized equity-based compensation during the period, that is, the amount recognized as expense in the income statement (or as asset if compensation is capitalized). Alternate captions include the words "stock-based compensation".

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Amount of increase in additional paid in capital (APIC) resulting from a tax benefit associated with share-based compensation plan other than an employee stock ownership plan (ESOP). Includes, but is not limited to, excess tax benefit.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Decrease in noncontrolling interest balance from payment of dividends or other distributions by the non-wholly owned subsidiary or partially owned entity, included in the consolidation of the parent entity, to the noncontrolling interest holders.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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Number of shares issued during the period as a result of the conversion of convertible securities.

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Value of stock (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of stock value of such awards forfeited. Stock issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (USD $) In Millions, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock at Cost	Non-Controlling Interests
Beginning Balance at Dec. 31, 2011	$ 2,499.6	$ 0.5	$ 927.5	$ 50.0	$ 1,176.7	$ (288.7)	$ 633.6
Beginning balance (in shares) at Dec. 31, 2011	53.9us-gaap_CommonStockSharesOutstanding
Increase (Decrease) in Stockholders' Equity
Net income	411.4us-gaap_ProfitLoss				174.0		237.4
Share-based compensation	25.4		25.4
Common stock issued under share-based incentive plans	73.0		(62.0)			135.0
Tax benefit from share-based incentive plans	25.5		25.5
Affiliate equity activity	(26.0)amg_ChangesInAffiliateEquity		(47.9)				21.9
Investments in Affiliates	247.6amg_InvestmentsInAffiliates						247.6
Shares repurchases	(60.9)					(60.9)
Distributions to non-controlling interests	(185.5)						(185.5)
Other comprehensive income (loss)	31.3			29.1			2.2
Ending Balance at Dec. 31, 2012	3,041.4	0.5	868.5	79.1	1,350.7	(214.6)	957.2
Ending balance (in shares) at Dec. 31, 2012	53.9us-gaap_CommonStockSharesOutstanding
Increase (Decrease) in Stockholders' Equity
Net income	669.6us-gaap_ProfitLoss				360.5		309.1
Share-based compensation	27.5		27.5
Common stock issued under share-based incentive plans	45.7		(53.2)			98.9
Tax benefit from share-based incentive plans	20.7		20.7
Settlement of convertible securities	(130.7)		(130.7)
Forward equity	(44.0)		(44.0)
Affiliate equity activity	(195.7)amg_ChangesInAffiliateEquity		(208.9)				13.2
Shares repurchases	(15.7)					(15.7)
Distributions to non-controlling interests	(267.1)						(267.1)
Other comprehensive income (loss)	(7.1)			(5.1)			(2.0)
Ending Balance at Dec. 31, 2013	3,144.6	0.5	479.9	74.0	1,711.2	(131.4)	1,010.4
Ending balance (in shares) at Dec. 31, 2013	53.9us-gaap_CommonStockSharesOutstanding
Increase (Decrease) in Stockholders' Equity
Net income	785.6us-gaap_ProfitLoss				452.1		333.5
Share-based compensation	29.3		29.3
Common stock issued under share-based incentive plans	(5.3)		(134.4)			129.1
Tax benefit from share-based incentive plans	60.2		60.2
Settlement of convertible securities (in shares)	1.9
Settlement of convertible securities	276.5	0.1	276.4
Forward equity	(45.0)		(45.0)
Affiliate equity activity	28.6amg_ChangesInAffiliateEquity		5.8				22.8
Investments in Affiliates	235.0amg_InvestmentsInAffiliates						235.0
Shares repurchases	(238.6)					(238.6)
Distributions to non-controlling interests	(569.4)						(569.4)
Other comprehensive income (loss)	(58.3)			(42.2)			(16.1)
Ending Balance at Dec. 31, 2014	$ 3,643.2	$ 0.6	$ 672.2	$ 31.8	$ 2,163.3	$ (240.9)	$ 1,016.2
Ending balance (in shares) at Dec. 31, 2014	55.8us-gaap_CommonStockSharesOutstanding