American Axle & Manufacturing (AXL) 10-Q 31 Jul 20 2020 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2020	Jul. 28, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	1-14303
Entity Registrant Name	AMERICAN AXLE & MANUFACTURING HOLDINGS, INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	38-3161171
Entity Address, Address Line One	One Dauch Drive
Entity Address, City or Town	Detroit
Entity Address, State or Province	MI
Entity Address, Postal Zip Code	48211-1198
City Area Code	313
Local Phone Number	758-2000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	AXL
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding (in shares)		113,272,990
Entity Central Index Key	0001062231
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net sales	$ 515.3	$ 1,704.3	$ 1,858.8	$ 3,423.5
Cost of goods sold	614.2	1,456	1,762.4	2,953
Gross profit (loss)	(98.9)	248.3	96.4	470.5
Selling, general and administrative expenses	73.8	91.3	164.1	182
Amortization of intangible assets	21.6	24.9	43.4	49.9
Impairment charge	0	0	510	0
Restructuring and acquisition-related costs	11.3	12.2	28.9	24.3
Loss on sale of business	0	0	1	0
Operating income (loss)	(205.6)	119.9	(651)	214.3
Interest expense	(54.6)	(56.2)	(106.1)	(109.6)
Interest income	3	0.5	5.8	1.2
Debt refinancing and redemption costs	0	(2.4)	(1.5)	(2.4)
Other income (expense), net	0.1	(3.1)	(2.2)	(6.1)
Income (loss) before income taxes	(257.1)	58.7	(755)	97.4
Income tax expense (benefit)	(43.9)	6	(40.6)	3
Net income (loss)	(213.2)	52.7	(714.4)	94.4
Net income attributable to noncontrolling interests	0	(0.2)	(0.1)	(0.3)
Net income (loss) attributable to AAM	$ (213.2)	$ 52.5	$ (714.5)	$ 94.1
Basic earnings (loss) per share	$ (1.88)	$ 0.45	$ (6.33)	$ 0.81
Diluted earnings (loss) per share	$ (1.88)	$ 0.45	$ (6.33)	$ 0.81

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net income (loss)	$ (213.2)	$ 52.7	$ (714.4)	$ 94.4
Other comprehensive income (loss)
Defined benefit plans, net of tax	1.7	1.1	3.3	1.8
Foreign currency translation adjustments	4.8	4.9	(44)	2.4
Changes in cash flow hedges, net of tax	8.7	(15.8)	(26)	(18.3)
Other comprehensive income (loss)	15.2	(9.8)	(66.7)	(14.1)
Comprehensive income (loss)	(198)	42.9	(781.1)	80.3
Net income attributable to noncontrolling interests	0	(0.2)	(0.1)	(0.3)
Foreign currency translation adjustments attributable to noncontrolling interests	0	0	0.3	0
Comprehensive income (loss) attributable to AAM	$ (198)	$ 42.7	$ (780.9)	$ 80

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other comprehensive income (loss), pension and other postretirement benefit plans, tax	$ (0.4)	$ (0.2)	$ (0.8)	$ (0.5)
Other comprehensive income (loss), derivatives qualifying as hedges, tax	$ (0.5)	$ 4.7	$ 1.8	$ 6.2

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 893.3	$ 532
Accounts receivable, net	550.2	815.4
Inventories, net	358.5	373.6
Prepaid expenses and other	159.5	136.8
Total current assets	1,961.5	1,857.8
Property, plant and equipment, net	2,209.9	2,358.4
Deferred income taxes	101.9	64.1
Goodwill	181.9	699.1
Other intangible assets, net	821.8	864.5
GM postretirement cost sharing asset	223.3	223.3
Other assets and deferred charges	554.7	577.4
Total assets	6,055	6,644.6
Current liabilities
Borrowings under Revolving Credit Facility	200	0
Current portion of long-term debt	373.7	28.7
Accounts payable	353.2	623.5
Accrued compensation and benefits	139.8	154.4
Deferred revenue	22.5	18.9
Accrued expenses and other	171.1	200.9
Total current liabilities	1,260.3	1,026.4
Long-term debt, net	3,561.4	3,612.3
Deferred revenue	78.5	83.7
Deferred income taxes	44.6	19.6
Postretirement benefits and other long-term liabilities	911.4	922.2
Total liabilities	5,856.2	5,664.2
Stockholders' equity
Common stock, par value $0.01 per share; 150.0 million shares authorized; 121.3 million shares issued as of June 30, 2020 and 120.2 million shares issued as of December 31, 2019	1.2	1.2
Paid-in capital	1,323.2	1,313.9
Retained earnings (Accumulated deficit)	(473)	248.6
Treasury stock at cost, 8.0 million shares as of June 30, 2020 and 7.6 million shares as of December 31, 2019	(212)	(209.3)
Accumulated other comprehensive loss
Defined benefit plans, net of tax	(256.6)	(259.9)
Foreign currency translation adjustments	(144.9)	(101.2)
Unrecognized loss on cash flow hedges, net of tax	(41.7)	(15.7)
Total AAM stockholders' equity	196.2	977.6
Noncontrolling interests in subsidiaries	2.6	2.8
Total stockholders' equity	198.8	980.4
Total liabilities and stockholders' equity	$ 6,055	$ 6,644.6

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares shares in Millions	Jun. 30, 2020	Dec. 31, 2019
Common stock, par or stated value per share	$ 0.01	$ 0.01
Common stock, shares authorized	150	150
Common stock, shares, issued	121.3	120.2
Treasury stock, shares	8	7.6

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Net income (loss)	$ (714.4)	$ 94.4
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Depreciation and amortization	268.7	277.3
Impairment charge	510	0
Deferred income taxes	(11.2)	(31.8)
Stock-based compensation	9.3	11.2
Pensions and other postretirement benefits, net of contributions	(2.5)	(9.5)
Loss on disposal of property, plant and equipment, net	11.9	1.1
Debt refinancing and redemption costs	1.5	2.4
Changes in operating assets and liabilities
Accounts receivable	256.6	(170.5)
Inventories	10.3	0
Accounts payable and accrued expenses	(298)	24.5
Deferred revenue	(1.5)	0.1
Other assets and liabilities	(43.8)	(62.3)
Net cash provided by (used in) operating activities	(3.1)	136.9
Investing activities
Purchases of property, plant and equipment	(105.6)	(237.5)
Proceeds from sale of property, plant and equipment	1.4	1.7
Investment in joint venture	0	(2.2)
Purchase buyouts of leased equipment	(0.2)	0
Final settlement on sale of business	(4.4)	0
Net cash used in investing activities	(108.8)	(238)
Financing activities
Proceeds from Revolving Credit Facility	350	0
Payments of Revolving Credit Facility	(150)	0
Proceeds from issuance of long-term debt	408.8	8
Payments of long-term debt	(115.6)	(128.2)
Debt issuance costs	(10.6)	0
Purchase of treasury stock	(2.7)	(7.5)
Other financing activities	0.3	0
Net cash provided by (used in) financing activities	480.2	(127.7)
Effect of exchange rate changes on cash	(7)	1.2
Net increase (decrease) in cash, cash equivalents and restricted cash	361.3	(227.6)
Cash, cash equivalents and restricted cash at beginning of period	532	478.9
Cash, cash equivalents and restricted cash at end of period	893.3	251.3
Supplemental cash flow information
Interest paid	102	102.1
Income taxes paid, net of refunds	$ 17.6	$ 34.6

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings (Accumulated Deficit)	Treasury Stock	AOCI Attributable to Parent	Noncontrolling Interest
Common stock, shares, outstanding at Dec. 31, 2018	111.7
Total AAM stockholders' equity at Dec. 31, 2018		$ 1.2	$ 1,292.6	$ 703.5	$ (201.8)	$ (311.6)	$ 2.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to AAM				41.6
Net income (loss) attributable to noncontrolling interest							0.1
Stock issued during period, shares, share-based compensation, net of forfeitures	1.2
Stock-based compensation			5.5
New accounting pronouncement, effect of adoption | ASU 2016-02 [Member]				1.9
New accounting pronouncement, effect of adoption | ASU 2018-02 [Member]				27.7		(27.7)
Treasury stock, shares, acquired	(0.4)
Purchase of treasury stock					(7.3)
Changes in cash flow hedges, net of tax						(2.5)
Foreign currency translation adjustments						(2.5)
Defined benefit plans, net of tax						0.7
Common stock, shares, outstanding at Mar. 31, 2019	112.5
Total AAM stockholders' equity at Mar. 31, 2019		1.2	1,298.1	774.7	(209.1)	(343.6)	2.5
Common stock, shares, outstanding at Dec. 31, 2018	111.7
Total AAM stockholders' equity at Dec. 31, 2018		1.2	1,292.6	703.5	(201.8)	(311.6)	2.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to AAM	$ 94.1
Net income (loss) attributable to noncontrolling interest	0.3
Purchase of treasury stock	7.5
Changes in cash flow hedges, net of tax	(18.3)
Foreign currency translation adjustments	2.4
Foreign currency translation adjustments attributable to noncontrolling interests	0
Defined benefit plans, net of tax	$ (1.8)
Common stock, shares, outstanding at Jun. 30, 2019	112.5
Total AAM stockholders' equity at Jun. 30, 2019		1.2	1,303.8	827.2	(209.3)	(353.4)	2.7
Common stock, shares, outstanding at Mar. 31, 2019	112.5
Total AAM stockholders' equity at Mar. 31, 2019		1.2	1,298.1	774.7	(209.1)	(343.6)	2.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to AAM	$ 52.5			52.5
Net income (loss) attributable to noncontrolling interest	$ 0.2						0.2
Stock-based compensation			5.7
Treasury stock, shares, acquired	0
Purchase of treasury stock					(0.2)
Changes in cash flow hedges, net of tax	$ (15.8)					(15.8)
Foreign currency translation adjustments	4.9					4.9
Foreign currency translation adjustments attributable to noncontrolling interests	0
Defined benefit plans, net of tax	$ (1.1)					1.1
Common stock, shares, outstanding at Jun. 30, 2019	112.5
Total AAM stockholders' equity at Jun. 30, 2019		1.2	1,303.8	827.2	(209.3)	(353.4)	2.7
Common stock, shares, outstanding at Dec. 31, 2019	112.6
Total AAM stockholders' equity at Dec. 31, 2019	$ 977.6	1.2	1,313.9	248.6	(209.3)	(376.8)	2.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to AAM				(501.3)
Net income (loss) attributable to noncontrolling interest							0.1
Stock issued during period, shares, share-based compensation, net of forfeitures	0.8
Stock-based compensation			4.6
New accounting pronouncement, effect of adoption | ASU 2016-13 [Member]				(7.1)
Treasury stock, shares, acquired	(0.4)
Purchase of treasury stock					(2.4)
Changes in cash flow hedges, net of tax						(34.7)
Foreign currency translation adjustments						(48.5)
Foreign currency translation adjustments attributable to noncontrolling interests							(0.3)
Defined benefit plans, net of tax						1.6
Common stock, shares, outstanding at Mar. 31, 2020	113
Total AAM stockholders' equity at Mar. 31, 2020		1.2	1,318.5	(259.8)	(211.7)	(458.4)	2.6
Common stock, shares, outstanding at Dec. 31, 2019	112.6
Total AAM stockholders' equity at Dec. 31, 2019	$ 977.6	1.2	1,313.9	248.6	(209.3)	(376.8)	2.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to AAM	(714.5)
Net income (loss) attributable to noncontrolling interest	0.1
Purchase of treasury stock	2.7
Changes in cash flow hedges, net of tax	(26)
Foreign currency translation adjustments	(44)
Foreign currency translation adjustments attributable to noncontrolling interests	(0.3)
Defined benefit plans, net of tax	$ (3.3)
Common stock, shares, outstanding at Jun. 30, 2020	113.3
Total AAM stockholders' equity at Jun. 30, 2020	$ 196.2	1.2	1,323.2	(473)	(212)	(443.2)	2.6
Common stock, shares, outstanding at Mar. 31, 2020	113
Total AAM stockholders' equity at Mar. 31, 2020		1.2	1,318.5	(259.8)	(211.7)	(458.4)	2.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to AAM	$ (213.2)			(213.2)
Net income (loss) attributable to noncontrolling interest	$ 0						0
Stock issued during period, shares, share-based compensation, net of forfeitures	0.3
Stock-based compensation			4.7
Treasury stock, shares, acquired	0
Purchase of treasury stock					(0.3)
Changes in cash flow hedges, net of tax	$ 8.7					8.7
Foreign currency translation adjustments	4.8					4.8
Foreign currency translation adjustments attributable to noncontrolling interests	0
Defined benefit plans, net of tax	$ (1.7)					1.7
Common stock, shares, outstanding at Jun. 30, 2020	113.3
Total AAM stockholders' equity at Jun. 30, 2020	$ 196.2	$ 1.2	$ 1,323.2	$ (473)	$ (212)	$ (443.2)	$ 2.6

Organization and Basis of Prese

Organization and Basis of Presentation (Notes)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	1. ORGANIZATION AND BASIS OF PRESENTATION Organization We are a global Tier 1 supplier to the automotive industry. We design, engineer and manufacture driveline and metal forming products that are making the next generation of vehicles smarter, lighter, safer and more efficient. We employ approximately 20,000 associates, operating at nearly 80 facilities in 17 countries, to support our customers on global and regional platforms with a continued focus on delivering quality, operational excellence and technology leadership. Basis of Presentation We have prepared the accompanying interim condensed consolidated financial statements in accordance with the instructions to Form 10-Q under the Securities Exchange Act of 1934. These condensed consolidated financial statements are unaudited but include all normal recurring adjustments, which we consider necessary for a fair presentation of the information set forth herein. Results of operations for the periods presented are not necessarily indicative of the results for the full fiscal year. The balance sheet at December 31, 2019 presented herein has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by accounting principles generally accepted in the United States of America (GAAP) for complete consolidated financial statements. In order to prepare the accompanying interim condensed consolidated financial statements, we are required to make estimates and assumptions that affect the reported amounts and disclosures in our interim condensed consolidated financial statements. These estimates and assumptions are impacted by risks and uncertainties, including those associated with the Novel Coronavirus (COVID-19) pandemic that began in the first quarter of 2020. While we have made estimates and assumptions based on the facts and circumstances available as of the date of this report, the full impact of COVID-19 cannot be predicted, and actual results could differ materially from those estimates and assumptions. For further information, refer to the audited consolidated financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2019. Effect of New Accounting Standards and Other Regulatory Pronouncements Accounting Standard Update 2020-04 On March 12, 2020, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2020-04 - Reference Rate Reform (Topic 848) . This guidance provides optional expedients and exceptions that are intended to ease the burden of updating contracts to contain a new reference rate due to the discontinuation of the London Inter-Bank Offered Rate (LIBOR). This guidance is available immediately and may be implemented in any period prior to the guidance expiration on December 31, 2022. We are currently assessing which of our various contracts will require an update for a new reference rate and will determine the timing for our implementation of this guidance at the completion of that analysis. Accounting Standard Update 2019-12 On December 18, 2019, the FASB issued ASU 2019-12 - Income Taxes (Topic 740) . This guidance is intended to simplify the accounting and disclosure requirements for income taxes by removing various exceptions and requires that the effect of an enacted change in tax laws or rates be included in the annual effective tax rate computation in the interim period of the enactment. This guidance becomes effective at the beginning of our 2021 fiscal year. We expect to adopt this guidance on January 1, 2021 and we are currently assessing the impact that this standard will have on our consolidated financial statements. Accounting Standards Update 2016-13 On June 16, 2016, the FASB issued 2016-13 - Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . ASU 2016-13 replaces the incurred loss model under previous guidance, and requires entities to consider expected credit losses, in addition to past events and current conditions when measuring credit losses. This guidance applies to certain of our financial instruments and is primarily applicable to our trade accounts receivable. We adopted this guidance on January 1, 2020, using a modified-retrospective transition method and the adoption of this standard did not have a material impact on our condensed consolidated financial statements. See the Statement of Stockholders' Equity for the implementation impact of ASU 2016-13. Securities and Exchange Commission (SEC) Rule In the first quarter of 2020, the SEC adopted "Financial Disclosures about Guarantors and Issuers of Guaranteed Securities and Affiliates Whose Securities Collateralize a Registrant's Securities," a rule that amends the financial disclosure requirements for guarantors and issuers of registered guaranteed securities. This rule eliminates the previous requirement to present guarantor financial statement information in the notes to the financial statements and allows for the disclosure of summarized financial information for the most recent year and interim period, as well as expanded non-financial disclosures, in Management's Discussion and Analysis (MD&A). The effective date for this rule is January 4, 2021, however, the SEC permitted voluntary compliance prior to this date and we elected to adopt the new disclosure requirements in the first quarter of 2020. As such, we no longer present guarantor financial statement information in the notes to the condensed consolidated financial statements in this Quarterly Report on Form 10-Q, but instead present the required information within MD&A. Coronavirus Aid, Relief, and Economic Security Act The Coronavirus Aid, Relief, and Economic Security Act (the CARES Act) was enacted on March 27, 2020 in the United States. The key provisions of the CARES Act, as applicable to AAM, include the following: • The ability to use net operating losses (NOLs) to offset income without the 80% taxable income limitation enacted as part of the Tax Cuts and Jobs Act (TCJA) of 2017, and to carry back NOLs to offset prior year income for five years. These are temporary provisions that apply to NOLs incurred in 2018, 2019 or 2020 tax years. • The ability to claim a current deduction for interest expense up to 50% of Adjusted Taxable Income (ATI) for tax years 2019 and 2020. This limitation was previously 30% of ATI pursuant to the TCJA, and will revert to 30% after 2020. • The ability to defer the payment of the employer portion of social security taxes incurred between March 27, 2020 and December 31, 2020, with 50% of the deferred amount to be paid by December 31, 2021 and the remaining 50% to be paid by December 31, 2022.

Restructuring and Acquisition-R

Restructuring and Acquisition-Related Costs (Notes)	6 Months Ended
	Jun. 30, 2020
Restructuring and Related Activities [Abstract]
Business Acquisition, Integration, Restructuring and Other Related Costs [Text Block]	2. RESTRUCTURING AND ACQUISITION-RELATED COSTS In the first quarter of 2019, we initiated a global restructuring program (the 2019 Program). The primary objectives of the 2019 Program were to further the integration of Metaldyne Performance Group, Inc. (MPG), align AAM's product and process technologies, and to achieve efficiencies within our corporate and business unit support teams to reduce cost in our business. In the first quarter of 2020, we initiated a new global restructuring program (the 2020 Program) that supersedes the 2019 Program. The primary objectives of the 2020 Program are to achieve efficiencies within our corporate and business unit support teams to reduce cost in our business, and to structurally adjust our operations to a new level of market demand based on the impact of COVID-19. We expect to incur costs under the 2020 Program through 2021. A summary of our restructuring activity for the first six months of 2020 and 2019 is shown below: Severance Charges Implementation Costs Total (in millions) Accrual at December 31, 2018 $ 2.4 $ 1.6 $ 4.0 Charges 8.2 8.9 17.1 Cash utilization (7.9) (7.1) (15.0) Accrual at June 30, 2019 $ 2.7 $ 3.4 $ 6.1 Accrual at December 31, 2019 $ 4.8 $ 7.4 $ 12.2 Charges 16.3 7.7 24.0 Cash utilization (16.0) (8.9) (24.9) Accrual at June 30, 2020 $ 5.1 $ 6.2 $ 11.3 As part of our restructuring actions, we incurred total severance charges of approximately $16.3 million and $8.2 million during the six months ended June 30, 2020 and 2019, respectively. We also incurred total implementation costs of approximately $7.7 million and $8.9 million during the six months ended June 30, 2020 and 2019, respectively. Implementation costs in both periods consist primarily of plant exit costs. Approximately $16.2 million of the restructuring costs incurred during the six months ended June 30, 2020 were under the 2020 Program. Approximately $9.9 million and $10.4 million of our total restructuring costs for the six months ended June 30, 2020 related to our Driveline and Metal Forming segments, respectively, while the remainder were corporate costs. Approximately $1.5 million, $9.8 million and $0.7 million of our total restructuring costs for the six months ended June 30, 2019 related to our Driveline, Metal Forming and former Casting segments, respectively, while the remainder were corporate costs. We expect to incur approximately $70 million to $80 million of total restructuring charges in 2020, including costs incurred under the 2020 Program. During the six months ended June 30, 2020 and 2019, we incurred the following integration charges primarily related to the integration of MPG: Integration Expenses (in millions) Charges for the six months ended June 30, 2020 $ 4.9 Charges for the six months ended June 30, 2019 7.2 These integration expenses primarily reflect costs incurred for information technology infrastructure and enterprise resource planning systems. Total restructuring charges and acquisition-related charges are presented on a separate line item titled Restructuring and acquisition-related costs in our Condensed Consolidated Statements of Operations, and totaled $11.3 million and $28.9 million for the three and six months ended June 30, 2020, respectively, and $12.2 million and $24.3 million for the three and six months ended June 30, 2019, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Notes)	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets Disclosure [Text Block]	3. GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill The following table provides a reconciliation of changes in goodwill for the six months ended June 30, 2020: Driveline Metal Forming Consolidated (in millions) Balance at December 31, 2019 $ 398.3 $ 300.8 $ 699.1 Impairment charge (210.8) (299.2) (510.0) Foreign currency translation (5.6) (1.6) (7.2) Balance at June 30, 2020 $ 181.9 $ — $ 181.9 In the first quarter of 2020, the reduction in global automotive production volumes caused by the impact of COVID-19 represented an indicator to test our goodwill for impairment. This reduction in production volumes began in March of 2020 and resulted in lower forecasted sales volumes in the periods included in our long-range plan as revised in the first quarter of 2020. In performing this test, we utilize a third-party valuation specialist to assist management in determining the fair value of our reporting units. Fair value of each reporting unit is estimated based on a combination of discounted cash flows and the use of pricing multiples derived from an analysis of comparable public companies multiplied against historical and/or anticipated financial metrics of each reporting unit. These calculations contain uncertainties as they require management to make assumptions including, but not limited to, market comparables, future cash flows of the reporting units, and appropriate discount and long-term growth rates. This fair value determination is categorized as Level 3 within the fair value hierarchy. As a result of this goodwill impairment test in the first quarter of 2020, we determined that the carrying values of both our Driveline and Metal Forming reporting units were greater than their respective fair values. As such, we recorded a goodwill impairment charge of $210.8 million associated with our Driveline reporting unit and a goodwill impairment charge of $299.2 million associated with our Metal Forming reporting unit in the first quarter of 2020. The Metal Forming impairment charge represented a full impairment of the goodwill associated with that reporting unit. These impairment charges were primarily the result of a decline in the projected cash flows of these reporting units under our revised long-range plan completed in the first quarter of 2020. The revision to our long-range plan was driven by lower forecasted sales volumes in the internal and external data sources used to form our projections primarily due to the reduction in global automotive production volumes caused by the impact of COVID-19. The impairment charges were also the result of changes in certain market-related inputs to the analysis to reflect macro-economic changes caused by the impact of COVID-19, including increased discount rates and lower pricing multiples for comparable public companies. At June 30, 2020, accumulated goodwill impairment losses were $1,435.5 million. The reduction in production volumes and changes to macro-economic factors caused by the impact of COVID-19 also represented an indicator to test our long-lived assets, including other intangible assets and property, plant and equipment, for impairment. We completed this test in the first quarter of 2020 and there was no impairment of these assets. Other Intangible Assets The following table provides a reconciliation of the gross carrying amount and associated accumulated amortization for AAM's other intangible assets, which are all subject to amortization: June 30, December 31, 2020 2019 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount (in millions) Capitalized computer software $ 46.1 $ (30.8) $ 15.3 $ 45.8 $ (27.6) $ 18.2 Customer platforms 856.2 (206.1) 650.1 856.2 (174.4) 681.8 Customer relationships 53.0 (11.1) 41.9 53.0 (9.4) 43.6 Technology and other 156.0 (41.5) 114.5 156.0 (35.1) 120.9 Total $ 1,111.3 $ (289.5) $ 821.8 $ 1,111.0 $ (246.5) $ 864.5

Inventories (Notes)

Inventories (Notes)	6 Months Ended
	Jun. 30, 2020
Inventory Disclosure [Abstract]
Inventory Disclosure [Text Block]	4. INVENTORIES We state our inventories at the lower of cost or net realizable value. The cost of our inventories is determined using the first-in first-out method. When we determine that our gross inventories exceed usage requirements, or if inventories become obsolete or otherwise not saleable, we record a provision for such loss as a component of our inventory accounts. Inventories consist of the following: June 30, 2020 December 31, 2019 (in millions) Raw materials and work-in-progress $ 305.5 $ 310.4 Finished goods 81.1 83.7 Gross inventories 386.6 394.1 Inventory valuation reserves (28.1) (20.5) Inventories, net $ 358.5 $ 373.6

Long-Term Debt (Notes)

Long-Term Debt (Notes)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Long-term Debt [Text Block]	5. LONG-TERM DEBT Long-term debt consists of the following: June 30, 2020 December 31, 2019 (in millions) Revolving Credit Facility $ 200.0 $ — Term Loan A Facility 340.0 340.0 Term Loan B Facility 1,188.8 1,188.8 6.875% Notes due 2028 400.0 — 6.625% Notes due 2022 350.0 450.0 6.50% Notes due 2027 500.0 500.0 6.25% Notes due 2026 400.0 400.0 6.25% Notes due 2025 700.0 700.0 Foreign credit facilities and other 109.6 113.4 Total debt 4,188.4 3,692.2 Less: Borrowings under Revolving Credit Facility 200.0 — Less: Current portion of long-term debt 373.7 28.7 Long-term debt 3,614.7 3,663.5 Less: Debt issuance costs 53.3 51.2 Long-term debt, net $ 3,561.4 $ 3,612.3 Senior Secured Credit Facilities In 2017, American Axle & Manufacturing Holdings, Inc. (Holdings) and American Axle & Manufacturing, Inc. (AAM, Inc.) entered into a credit agreement (the Credit Agreement). In connection with the Credit Agreement, Holdings, AAM, Inc. and certain of their restricted subsidiaries entered into a Collateral Agreement and Guarantee Agreement with the financial institutions party thereto. The Credit Agreement included a $100.0 million term loan A facility (the Term Loan A Facility), a $1.55 billion term loan B facility (the Term Loan B Facility) and a $932 million multi-currency revolving credit facility (the Revolving Credit Facility, and together with the Term Loan A Facility and the Term Loan B Facility, the Senior Secured Credit Facilities). In July 2019, Holdings, AAM, Inc., and certain subsidiaries of Holdings entered into the First Amendment (First Amendment) to the Credit Agreement. The First Amendment, among other things, established $340 million in incremental term loan A commitments with a maturity date of July 29, 2024 (Term Loan A Facility due 2024), reduced the availability under the Revolving Credit Facility from $932 million to $925 million, and extended the maturity date of the Revolving Credit Facility from April 6, 2022 to July 29, 2024, and modified the applicable margin with respect to interest rates under the Term Loan A Facility due 2024 and interest rates and commitment fees under the Revolving Credit Facility. The applicable margin and the maturity date for the Term Loan B Facility remain unchanged. The proceeds of $340 million were used to repay all of the outstanding loans under the existing Term Loan A Facility and a portion of the outstanding Term Loan B Facility, resulting in no additional indebtedness. This also satisfies all payment requirements under the Term Loan B Facility until maturity in 2024. In April 2020, Holdings, AAM, Inc., and certain subsidiaries of Holdings entered into the Second Amendment (Second Amendment) to the Credit Agreement. For the period from April 1, 2020 through March 31, 2022 (the Amendment Period), the Second Amendment, among other things, replaced the total net leverage ratio covenant with a new senior secured net leverage ratio covenant, reduced the minimum levels of the cash interest expense coverage ratio covenant, and modified certain covenants restricting the ability of Holdings, AAM and certain subsidiaries of Holdings to create, incur, assume or permit to exist certain additional indebtedness and liens and to make certain restricted payments, voluntary payments and distributions. The Second Amendment also increased the maximum levels of the total net leverage ratio covenant after the Amendment Period, modified the applicable margin with respect to interest rates under the Term Loan A Facility due 2024 and interest rates and commitment fees under the Revolving Credit Facility, and increased the minimum adjusted London Interbank Offered Rate for Eurodollar-based loans under the Term Loan A Facility due 2024 and Revolving Credit Facility. The applicable margin for the Term Loan B Facility remains unchanged. We paid debt issuance costs of $4.6 million in the six months ended June 30, 2020 related to the Second Amendment. At June 30, 2020, we had $691.4 million available under the Revolving Credit Facility. This availability reflects $200.0 million of borrowings and $33.6 million for standby letters of credit issued against the facility. The proceeds of the Revolving Credit Facility are used for general corporate purposes. The Senior Secured Credit Facilities provide back-up liquidity for our foreign credit facilities. We intend to use the availability of long-term financing under the Senior Secured Credit Facilities to refinance any current maturities related to such debt agreements that are not otherwise refinanced on a long-term basis in their local markets, except where otherwise reclassified to Current portion of long-term debt on our Condensed Consolidated Balance Sheet. 6.875% Notes due 2028 In June 2020, we issued $400 million in aggregate principal amount of 6.875% senior notes due 2028 (the 6.875% Notes). Proceeds from the 6.875% Notes will be used primarily to fund the redemption of the remaining $350 million of 6.625% senior notes due 2022 described below and for general corporate purposes. We paid debt issuance costs of $6.0 million in the six months ended June 30, 2020 related to the 6.875% Notes. Redemption of 6.625% Notes due 2022 In the first quarter of 2020, we voluntarily redeemed a portion of our 6.625% Notes due 2022. This resulted in a principal payment of $100 million and $2.0 million in accrued interest. We also expensed approximately $0.4 million for the write-off of the unamortized debt issuance costs that we had been amortizing over the expected life of the borrowing, and approximately $1.1 million for an early redemption premium. In the second quarter of 2020, we issued an irrevocable notice to the holders of our 6.625% Notes due 2022 to voluntarily redeem the remaining portion of our 6.625% Notes due 2022 in the third quarter of 2020. In July 2020 this resulted in a principal payment of $350 million and $5.7 million in accrued interest. Subsequent to June 30, 2020, we expensed approximately $1.3 million for the write-off of the unamortized debt issuance costs that we had been amortizing over the expected life of the borrowing, and approximately $3.9 million for the payment of an early redemption premium. Foreign credit facilities We utilize local currency credit facilities to finance the operations of certain foreign subsidiaries. At June 30, 2020, $109.6 million was outstanding under our foreign credit facilities, as compared to $106.0 million at December 31, 2019. At June 30, 2020, an additional $78.9 million was available under our foreign credit facilities.

Derivatives (Notes)

Derivatives (Notes)	6 Months Ended
	Jun. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]	6. DERIVATIVES Our business and financial results are affected by fluctuations in global financial markets, including interest rates and currency exchange rates. Our hedging policy has been developed to manage these risks to an acceptable level based on management’s judgment of the appropriate trade-off between risk, opportunity and cost. We do not hold financial instruments for trading or speculative purposes. Currency derivative contracts From time to time, we use foreign currency forward contracts to reduce the effects of fluctuations in exchange rates relating to certain foreign currencies. As of June 30, 2020, we have currency forward contracts outstanding with a total notional amount of $144.7 million that hedge our exposure to changes in foreign currency exchange rates for certain payroll expenses into the first quarter of 2023 and other items into the fourth quarter of 2020. Fixed-to-fixed cross-currency swap In 2019, we entered into a fixed-to-fixed cross-currency swap to reduce the variability of functional currency equivalent cash flows associated with changes in exchange rates on certain Euro-based intercompany loans. In the first quarter of 2020, we discontinued this fixed-to-fixed cross-currency swap, which was in an asset position of $9.8 million on the date that it was discontinued. Also in the first quarter of 2020, we entered into a new fixed-to-fixed cross-currency swap to reduce the variability of functional currency equivalent cash flows associated with changes in exchange rates on certain Euro-based intercompany loans. As of June 30, 2020, the notional amount of the fixed-to-fixed cross-currency swap was $224.7 million, and hedges our exposure to changes in exchange rates on the intercompany loans into the second quarter of 2024. Variable-to-fixed interest rate swap In 2019, we entered into a variable-to-fixed interest rate swap to reduce the variability of cash flows associated with interest payments on our variable rate debt. We have the following notional amounts hedged in relation to our variable-to-fixed interest rate swap: $900.0 million through May 2021, $750.0 million through May 2022, $600.0 million through May 2023 and $500.0 million through May 2024. The following table summarizes the reclassification of derivative gains and losses into net income from accumulated other comprehensive income (loss) for those derivative instruments designated as cash flow hedges under ASC 815 - Derivatives and Hedging : Location Gain (Loss) Reclassified During Total of Financial Gain (Loss) Expected of Gain (Loss) Three Months Ended Six Months Ended Statement to be Reclassified Reclassified into June 30, June 30, Line Item During the Net Income 2020 2019 2020 2019 2020 Next 12 Months (in millions) Currency forward contracts Cost of Goods Sold $ (2.3) $ 0.7 $ (1.0) $ 0.9 $ 1,762.4 $ (5.8) Fixed-to-fixed cross-currency swap Other Income (Expense), net (3.7) — — — (2.2) 1.7 Variable-to-fixed interest rate swap Interest Expense (4.0) 0.7 (6.0) 1.9 (106.1) (16.2) See Note 12 - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (AOCI) for amounts recognized in other comprehensive income (loss) during the three and six months ended June 30, 2020 and 2019. The following table summarizes the amount and location of gains and losses recognized in the Condensed Consolidated Statements of Operations for those derivative instruments not designated as hedging instruments under ASC 815: Gain (Loss) Recognized During Total of Financial Location of Gain (Loss) Three Months Ended Six Months Ended Statement Line Recognized in June 30, June 30, Item Net Income 2020 2019 2020 2019 2020 (in millions) Currency forward contracts Cost of Goods Sold $ 0.8 $ 0.6 $ (7.6) $ 1.8 $ 1,762.4 Currency forward contracts Other Income (Expense), net (0.1) (0.4) (0.5) (0.6) (2.2)

Fair Value (Notes)

Fair Value (Notes)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Disclosures [Text Block]	7. FAIR VALUE ASC 820 - Fair Value Measurement defines fair value as “the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.” The definition is based on an exit price rather than an entry price, regardless of whether the entity plans to hold or sell the asset. This guidance also establishes a fair value hierarchy to prioritize inputs used in measuring fair value as follows: • Level 1: Observable inputs such as quoted prices in active markets; • Level 2: Inputs, other than quoted prices in active markets, that are observable either directly or indirectly; and • Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. Financial instruments The estimated fair value of our financial assets and liabilities that are recognized at fair value on a recurring basis, using available market information and other observable data, are as follows: June 30, 2020 December 31, 2019 Carrying Amount Fair Value Carrying Amount Fair Value Input (in millions) Balance Sheet Classification Cash equivalents $ 745.1 $ 745.1 $ 271.3 $ 271.3 Level 1 Prepaid expenses and other Cash flow hedges - currency forward contracts — — 5.0 5.0 Level 2 Cash flow hedges - variable-to-fixed interest rate swap 6.0 6.0 0.9 0.9 Level 2 Nondesignated - currency forward contracts — — 1.9 1.9 Level 2 Other assets and deferred charges Cash flow hedges - currency forward contracts 0.3 0.3 3.4 3.4 Level 2 Cash flow hedges - fixed-to-fixed cross-currency swap 2.9 2.9 1.1 1.1 Level 2 Cash flow hedges - variable-to-fixed interest rate swap 12.1 12.1 2.2 2.2 Level 2 Accrued expenses and other Cash flow hedges - currency forward contracts 5.8 5.8 — — Level 2 Cash flow hedges - variable-to-fixed interest rate swap 20.0 20.0 7.9 7.9 Level 2 Nondesignated - currency forward contracts 3.1 3.1 — — Level 2 Postretirement benefits and other long-term liabilities Cash flow hedges - currency forward contracts 5.0 5.0 — — Level 2 Cash flow hedges - variable-to-fixed interest rate swap 41.1 41.1 18.4 18.4 Level 2 The carrying values of our cash, accounts receivable, accounts payable and accrued liabilities approximate their fair values due to the short-term maturities of these instruments. The carrying values of our borrowings under the foreign credit facilities approximate their fair value due to the frequent resetting of the interest rates. We estimated the fair value of the amounts outstanding on our debt using available market information and other observable data, to be as follows: June 30, 2020 December 31, 2019 Carrying Amount Fair Value Carrying Amount Fair Value Input (in millions) Revolving Credit Facility $ 200.0 $ 200.0 $ — $ — Level 2 Term Loan A Facility 340.0 312.0 340.0 337.9 Level 2 Term Loan B Facility 1,188.8 1,123.5 1,188.8 1,174.0 Level 2 6.875% Notes due 2028 400.0 394.0 — — Level 2 6.625% Notes due 2022 350.0 354.0 450.0 455.4 Level 2 6.50% Notes due 2027 500.0 482.5 500.0 516.3 Level 2 6.25% Notes due 2026 400.0 384.0 400.0 409.0 Level 2 6.25% Notes due 2025 700.0 673.8 700.0 716.6 Level 2

Employee Benefit Plans (Notes)

Employee Benefit Plans (Notes)	6 Months Ended
	Jun. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Pension and Other Postretirement Benefits Disclosure [Text Block]	8. EMPLOYEE BENEFIT PLANS The components of net periodic benefit cost (credit) are as follows: Pension Benefits Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (in millions) Service cost $ 0.5 $ 0.4 $ 1.0 $ 0.7 Interest cost 5.4 7.1 10.8 14.2 Expected asset return (9.7) (10.3) (19.3) (20.6) Amortized loss 2.2 1.5 4.3 3.2 Net periodic benefit credit $ (1.6) $ (1.3) $ (3.2) $ (2.5) Other Postretirement Benefits Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (in millions) Service cost $ 0.1 $ 0.1 $ 0.2 $ 0.2 Interest cost 2.5 3.2 5.1 6.4 Amortized loss 0.3 — 0.5 0.1 Amortized prior service credit (0.4) (0.4) (0.8) (0.8) Net periodic benefit cost $ 2.5 $ 2.9 $ 5.0 $ 5.9 The noncurrent liabilities associated with our pension and other postretirement benefit plans are classified as Postretirement benefits and other long-term liabilities on our Condensed Consolidated Balance Sheets. As of June 30, 2020 and December 31, 2019, we have a noncurrent pension liability of $109.9 million and $118.2 million, respectively. As of June 30, 2020 and December 31, 2019, we have a noncurrent other postretirement benefits liability of $517.6 million and $520.0 million, respectively. Due to the availability of our pre-funded pension balances (previous contributions in excess of prior required pension contributions) related to certain of our U.S. pension plans, we expect our regulatory pension funding requirements in 2020 to be approximately $1.5 million. We expect our cash payments for other postretirement benefit obligations in 2020, net of GM cost sharing, to be approximately $17 million.

Product Warranties (Notes)

Product Warranties (Notes)	6 Months Ended
	Jun. 30, 2020
Product Warranties Disclosures [Abstract]
Product Warranty Disclosure [Text Block]	9. PRODUCT WARRANTIES We record a liability for estimated warranty obligations at the dates our products are sold. These estimates are established using sales volumes and internal and external warranty data where there is no payment history and historical information about the average cost of warranty claims for customers with prior claims. We estimate our costs based on the contractual arrangements with our customers, existing customer warranty terms and internal and external warranty data, which includes a determination of our warranty claims and actions taken to improve product quality and minimize warranty claims. We continuously evaluate these estimates and our customers' administration of their warranty programs. We monitor actual warranty claim data and adjust the liability, as necessary, on a quarterly basis. The following table provides a reconciliation of changes in the product warranty liability: Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (in millions) Beginning balance $ 64.2 $ 56.2 $ 62.0 $ 57.7 Accruals 0.6 5.0 4.8 9.4 Payments (0.7) (3.6) (2.0) (7.3) Adjustment to prior period accruals (0.4) (2.0) (0.5) (4.3) Foreign currency translation 0.2 0.1 (0.4) 0.2 Ending balance $ 63.9 $ 55.7 $ 63.9 $ 55.7

Income Taxes (Notes)

Income Taxes (Notes)	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	10. INCOME TAXES We adjust our effective tax rate each quarter based on our estimated annual effective tax rate. We also record the tax impact of certain discrete, unusual or infrequently occurring items, including changes in judgment about valuation allowances and effects of changes in tax laws or rates, in the interim period in which they occur. In addition, jurisdictions with a projected loss for the year or a year-to-date loss where no tax benefit can be recognized are excluded from the estimated annual effective tax rate. The impact of such an exclusion could result in a higher or lower effective tax rate during a particular quarter, based upon the mix and timing of actual earnings versus annual projections. Income tax was a benefit of $43.9 million for the three months ended June 30, 2020, an effective income tax rate of 17.1%, as compared to expense of $6.0 million for the three months ended June 30, 2019, an effective income tax rate of 10.2%. Income tax was a benefit of $40.6 million for the six months ended June 30, 2020, an effective income tax rate of 5.4%, as compared to expense of $3.0 million for the six months ended June 30, 2019, an effective income tax rate of 3.1%. In accordance with the guidance in ASC 740 - Income Taxes , we review the likelihood that we will realize the benefit of deferred tax assets and estimate whether recoverability of our deferred tax assets is "more likely than not" based on the available evidence. During the three months ended June 30, 2020, we determined that a portion of our deferred tax assets related to U.S. interest expense carryforwards were not more likely than not to be realized. As such, during the three months ended June 30, 2020, we recognized a tax expense of approximately $36.0 million to establish a partial valuation allowance in the U.S. Due to the uncertainty associated with the extent and ultimate impact of COVID-19 on global automotive production volumes, we may experience lower than projected earnings in certain jurisdictions in future periods, and it is reasonably possible that additional valuation allowances could be recognized in the next twelve months as a result. In addition, during the three months ended June 30, 2020, we finalized an advance pricing agreement in a foreign jurisdiction, which resulted in a tax benefit of approximately $6.8 million. Also during the three months ended June 30, 2020, we recognized a tax benefit of approximately $7.0 million related to our ability to carry back projected current year losses under the CARES Act to years with the previous 35% tax rate. This is in addition to a net tax benefit of approximately $7.5 million that we recognized in the first quarter of 2020 related to our ability to carry back losses from prior years under the CARES Act. See Note 1 - Organization and Basis of Presentation for additional detail regarding the CARES Act. Our effective income tax rates for the three and six months ended June 30, 2020 vary from our effective income tax rates for the three and six months ended June 30, 2019, as a result of the items discussed above. Further, our effective income tax rate for the six months ended June 30, 2020 varies from our effective income tax rate for the six months ended June 30, 2019 as a result of the impact of the goodwill impairment charge recorded during the first six months of 2020, which had no corresponding income tax benefit. In addition, in the first six months of 2019, we recognized an income tax benefit of $9.3 million related to final regulations issued by the Department of Treasury and Internal Revenue Service in the first quarter of 2019. The final regulations changed the manner in which we were required to compute the one-time transition tax under the TCJA that was imposed on certain foreign earnings for which U.S. income tax was previously deferred. For the three and six months ended June 30, 2020 and 2019, our effective income tax rates vary from the U.S. federal statutory rate primarily due to favorable foreign tax rates, the impact of tax credits, and the effect of the items described above. We operate in multiple jurisdictions throughout the world and the income tax returns of several subsidiaries in various tax jurisdictions are currently under examination. We are currently under a U.S. federal income tax examination for the years 2015 through 2018. Generally, we are no longer subject to U.S. federal, state and local, or non-U.S. income tax examinations by tax authorities for years prior to 2013. In the second quarter of 2020, we finalized an advance pricing agreement in a foreign jurisdiction, which resulted in a cash payment to the tax authorities of $18.5 million and a reduction of our liability for unrecognized tax benefits and related interest and penalties of $25.3 million.

Earnings Per Share (Notes)

Earnings Per Share (Notes)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	11. EARNINGS (LOSS) PER SHARE (EPS) We present EPS using the two-class method. This method allocates undistributed earnings between common shares and non-vested share based payment awards that entitle the holder to non-forfeitable dividend rights. Our participating securities include non-vested restricted stock units. The following table sets forth the computation of our basic and diluted EPS available to shareholders of common stock (excluding participating securities): Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (in millions, except per share data) Numerator Net income (loss) attributable to AAM $ (213.2) $ 52.5 $ (714.5) $ 94.1 Less: Net income attributable to participating securities — (1.5) — (2.7) Net income (loss) attributable to common shareholders - Basic and Dilutive $ (213.2) $ 51.0 $ (714.5) $ 91.4 Denominators Basic common shares outstanding - Weighted-average shares outstanding 118.4 115.8 117.4 115.6 Less: Participating securities (5.3) (3.3) (4.5) (3.4) Weighted-average common shares outstanding 113.1 112.5 112.9 112.2 Effect of dilutive securities - Dilutive stock-based compensation — 0.3 — 0.4 Diluted shares outstanding - Adjusted weighted-average shares after assumed conversions 113.1 112.8 112.9 112.6 Basic EPS $ (1.88) $ 0.45 $ (6.33) $ 0.81 Diluted EPS $ (1.88) $ 0.45 $ (6.33) $ 0.81

Reclassifications out of Accumu

Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Notes)	6 Months Ended
	Jun. 30, 2020
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Abstract]
Disclosure of Reclassification Amount [Text Block]	12. RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (AOCI) Reclassification adjustments and other activity impacting accumulated other comprehensive income (loss) during the three months ended June 30, 2020 and June 30, 2019 are as follows (in millions) : Defined Benefit Plans Foreign Currency Translation Adjustments Unrecognized Gain (Loss) on Cash Flow Hedges Total Balance at March 31, 2020 $ (258.3) $ (149.7) $ (50.4) $ (458.4) Other comprehensive income (loss) before reclassifications — 4.8 (0.8) 4.0 Income tax effect of other comprehensive income (loss) before reclassifications — — 1.2 1.2 Amounts reclassified from accumulated other comprehensive loss 2.1 (a) — 10.0 (b) 12.1 Income taxes reclassified into net income (0.4) — (1.7) (2.1) Net change in accumulated other comprehensive loss 1.7 4.8 8.7 15.2 Balance at June 30, 2020 $ (256.6) $ (144.9) $ (41.7) $ (443.2) Defined Benefit Plans Foreign Currency Translation Adjustments Unrecognized Gain (Loss) on Cash Flow Hedges Total Balance at March 31, 2019 $ (240.9) $ (99.1) $ (3.6) $ (343.6) Other comprehensive income (loss) before reclassifications — 4.9 (19.1) (14.2) Income tax effect of other comprehensive income (loss) before reclassifications — — 4.6 4.6 Amounts reclassified from accumulated other comprehensive loss 1.3 (a) — (1.4) (b) (0.1) Income taxes reclassified into net income (0.2) — 0.1 (0.1) Net change in accumulated other comprehensive loss 1.1 4.9 (15.8) (9.8) Balance at June 30, 2019 $ (239.8) $ (94.2) $ (19.4) $ (353.4) (a) These amounts were reclassified from AOCI to Other income (expense), net for the three months ended June 30, 2020 and June 30, 2019. (b) The amounts reclassified from AOCI included $2.3 million in cost of goods sold (COGS), $4.0 million in interest expense and $3.7 million in Other income (expense), net for the three months ended June 30, 2020 and $(0.7) million in COGS and $(0.7) million in interest expense for the three months ended June 30, 2019. Reclassification adjustments and other activity impacting accumulated other comprehensive income (loss) during the six months ended June 30, 2020 and June 30, 2019 are as follows (in millions) : Defined Benefit Plans Foreign Currency Translation Adjustments Unrecognized Gain (Loss) on Cash Flow Hedges Total Balance at December 31, 2019 $ (259.9) $ (101.2) $ (15.7) $ (376.8) Other comprehensive income (loss) before reclassifications — (43.7) (34.8) (78.5) Income tax effect of other comprehensive income (loss) before reclassifications — — 3.1 3.1 Amounts reclassified from accumulated other comprehensive loss 4.1 (a) — 7.0 (b) 11.1 Income taxes reclassified into net income (0.8) — (1.3) (2.1) Net change in accumulated other comprehensive loss 3.3 (43.7) (26.0) (66.4) Balance at June 30, 2020 $ (256.6) $ (144.9) $ (41.7) $ (443.2) Defined Benefit Plans Foreign Currency Translation Adjustments Unrecognized Gain (Loss) on Cash Flow Hedges Total Balance at December 31, 2018 $ (213.9) $ (96.6) $ (1.1) $ (311.6) Other comprehensive income (loss) before reclassifications (27.9) (c) 2.4 (21.7) (47.2) Income tax effect of other comprehensive income (loss) before reclassifications — — 5.8 5.8 Amounts reclassified from accumulated other comprehensive income (loss) 2.5 (a) — (2.8) (b) (0.3) Income taxes reclassified into net income (0.5) — 0.4 (0.1) Net change in accumulated other comprehensive income (loss) (25.9) 2.4 (18.3) (41.8) Balance at June 30, 2019 $ (239.8) $ (94.2) $ (19.4) $ (353.4) (a) These amounts were reclassified from AOCI to Other income (expense), net for the six months ended June 30, 2020 and June 30, 2019. (b) The amounts reclassified from AOCI included $1.0 million in COGS and $6.0 million in interest expense for the six months ended June 30, 2020 and $(0.9) million in COGS and $(1.9) million in interest expense for the six months ended June 30, 2019. (c) ASU 2018-02 became effective on January 1, 2019, and we elected to reclassify the stranded tax effects caused by the 2017 Tax Cuts and Jobs Act, resulting in a decrease in Accumulated other comprehensive income (loss) of $27.7 million at January 1, 2019.

Revenue from Contracts with Cus

Revenue from Contracts with Customers (Notes)	6 Months Ended
	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Text Block]	13. REVENUE FROM CONTRACTS WITH CUSTOMERS Net sales recognized from contracts with customers, disaggregated by segment and geographical location, are presented in the following table for the three and six months ended June 30, 2020 and 2019. Net sales are attributed to regions based on the location of production. Intersegment sales have been excluded from the table. In the fourth quarter of 2019, we completed the sale of the U.S operations of our former Casting segment (the Casting Sale). The Casting Sale did not include the entities that conduct AAM's casting operations in El Carmen, Mexico, which are now included in our Driveline segment. The Casting Sale did not qualify for classification as discontinued operations, as it did not represent a strategic shift in our business that has had, or will have, a major effect on our operations and financial results. As such, we continue to present Casting as a segment in the table below for the three and six months ended June 30, 2019, and the reported amounts are now comprised entirely of the U.S. casting operations that were included in the sale. The amounts previously reported in our Casting segment for the retained operations in El Carmen, Mexico have been reclassified to our Driveline segment for the three and six months ended June 30, 2019. Three Months Ended June 30, 2020 Driveline Metal Forming Casting Total North America $ 260.4 $ 83.7 $ — $ 344.1 Asia 88.1 10.0 — 98.1 Europe 46.3 24.5 — 70.8 South America 1.7 0.6 — 2.3 Total $ 396.5 $ 118.8 $ — $ 515.3 Three Months Ended June 30, 2019 Driveline Metal Forming Casting Total North America $ 903.9 $ 301.4 $ 171.3 $ 1,376.6 Asia 135.0 7.9 — 142.9 Europe 90.8 67.2 — 158.0 South America 25.9 0.9 — 26.8 Total $ 1,155.6 $ 377.4 $ 171.3 $ 1,704.3 Six Months Ended June 30, 2020 Driveline Metal Forming Casting Total North America $ 1,051.7 $ 345.3 $ — $ 1,397.0 Asia 191.2 16.1 — 207.3 Europe 145.2 85.7 — 230.9 South America 20.4 3.2 — 23.6 Total $ 1,408.5 $ 450.3 $ — $ 1,858.8 Six Months Ended June 30, 2019 Driveline Metal Forming Casting Total North America $ 1,771.9 $ 606.8 $ 353.7 $ 2,732.4 Asia 288.3 15.4 — 303.7 Europe 192.4 139.9 — 332.3 South America 51.7 3.4 — 55.1 Total $ 2,304.3 $ 765.5 $ 353.7 $ 3,423.5 Contract Assets and Liabilities The following table summarizes our beginning and ending balances for accounts receivable and contract liabilities associated with our contracts with customers: Accounts Receivable, Net Contract Liabilities (Current) Contract Liabilities (Long-term) December 31, 2019 $ 815.4 $ 18.9 $ 83.7 June 30, 2020 550.2 22.5 78.5 Increase/(decrease) $ (265.2) $ 3.6 $ (5.2) Contract liabilities relate to deferred revenue associated with various settlements and commercial agreements for which we have a future performance obligation to the customer. We recognize this deferred revenue into revenue over the life of the associated program as we satisfy our performance obligations to the customer. We do not have contract assets as defined in ASC 606. During the three and six months ended June 30, 2020, we amortized $5.2 million and $11.9 million, respectively, of previously recorded contract liabilities into revenue as we satisfied performance obligations with our customers.

Segment Reporting (Notes)

Segment Reporting (Notes)	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Segment Reporting Disclosure [Text Block]	14. SEGMENT REPORTING Our business is organized into Driveline and Metal Forming segments, with each representing a reportable segment under ASC 280 Segment Reporting . In the fourth quarter of 2019, we completed the Casting Sale, which did not include the entities that conduct AAM's casting operations in El Carmen, Mexico, which are now included in our Driveline segment. The Casting Sale did not qualify for classification as discontinued operations, as it did not represent a strategic shift in our business that has had, or will have, a major effect on our operations and financial results. As such, we continue to present Casting as a segment in the table below for the three and six months ended June 30, 2019, and the reported amounts are now comprised entirely of the U.S. casting operations that were included in the sale. The amounts previously reported in our Casting segment for the retained operations in El Carmen, Mexico have been reclassified to our Driveline segment for the three and six months ended June 30, 2019. The results of each segment are regularly reviewed by the chief operating decision maker to assess the performance of the segment and make decisions regarding the allocation of resources to the segments. Our product offerings by segment are as follows: • Driveline products consist primarily of front and rear axles, driveshafts, differential assemblies, clutch modules, balance shaft systems, disconnecting driveline technology, and electric and hybrid driveline products and systems for light trucks, sport utility vehicles (SUVs), crossover vehicles, passenger cars and commercial vehicles; and • Metal Forming products consist primarily of axle and transmission shafts, ring and pinion gears, differential gears and assemblies, connecting rods and variable valve timing products for Original Equipment Manufacturers and Tier 1 automotive suppliers. We use Segment Adjusted EBITDA as the measure of earnings to assess the performance of each segment and determine the resources to be allocated to the segments. We define EBITDA to be earnings before interest expense, income taxes, depreciation and amortization. Segment Adjusted EBITDA is defined as EBITDA for our reportable segments excluding the impact of restructuring and acquisition-related costs, debt refinancing and redemption costs, gain (loss) on the sale of a business, impairment charges, pension settlements and non-recurring items. The following tables represent information by reportable segment for the three months ended June 30, 2020 and 2019 (in millions) : Three Months Ended June 30, 2020 Driveline Metal Forming Casting Total Sales $ 403.7 $ 150.3 $ — $ 554.0 Less: intersegment sales 7.2 31.5 — 38.7 Net external sales $ 396.5 $ 118.8 $ — $ 515.3 Segment Adjusted EBITDA $ (31.2) $ (20.9) $ — $ (52.1) Three Months Ended June 30, 2019 Driveline Metal Forming Casting Total Sales $ 1,181.5 $ 484.2 $ 179.7 $ 1,845.4 Less: intersegment sales 25.9 106.8 8.4 141.1 Net external sales $ 1,155.6 $ 377.4 $ 171.3 $ 1,704.3 Segment Adjusted EBITDA $ 162.1 $ 86.5 $ 17.4 $ 266.0 The following tables represent information by reportable segment for the six months ended June 30, 2020 and 2019 (in millions) : Six Months Ended June 30, 2020 Driveline Metal Forming Casting Total Sales $ 1,435.4 $ 572.6 $ — $ 2,008.0 Less: intersegment sales 26.9 122.3 — 149.2 Net external sales $ 1,408.5 $ 450.3 $ — $ 1,858.8 Segment Adjusted EBITDA $ 108.1 $ 53.1 $ — $ 161.2 Six Months Ended June 30, 2019 Driveline Metal Forming Casting Total Sales $ 2,347.8 $ 967.5 $ 373.4 $ 3,688.7 Less: intersegment sales 43.5 202.0 19.7 265.2 Net external sales $ 2,304.3 $ 765.5 $ 353.7 $ 3,423.5 Segment Adjusted EBITDA $ 304.9 $ 170.9 $ 35.2 $ 511.0 The following table represents a reconciliation of Total Segment Adjusted EBITDA to consolidated income (loss) before income taxes for the three and six months ended June 30, 2020 and 2019 (in millions) : Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Total segment adjusted EBITDA $ (52.1) $ 266.0 $ 161.2 $ 511.0 Interest expense (54.6) (56.2) (106.1) (109.6) Depreciation and amortization (139.1) (136.5) (268.7) (277.3) Restructuring and acquisition-related costs (11.3) (12.2) (28.9) (24.3) Loss on sale of business — — (1.0) — Debt refinancing and redemption costs — (2.4) (1.5) (2.4) Impairment charge — — (510.0) — Income (loss) before income taxes $ (257.1) $ 58.7 $ (755.0) $ 97.4

Organization and Basis of Pre_2

Organization and Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting, Policy [Policy Text Block]	Basis of Presentation We have prepared the accompanying interim condensed consolidated financial statements in accordance with the instructions to Form 10-Q under the Securities Exchange Act of 1934. These condensed consolidated financial statements are unaudited but include all normal recurring adjustments, which we consider necessary for a fair presentation of the information set forth herein. Results of operations for the periods presented are not necessarily indicative of the results for the full fiscal year. The balance sheet at December 31, 2019 presented herein has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by accounting principles generally accepted in the United States of America (GAAP) for complete consolidated financial statements. In order to prepare the accompanying interim condensed consolidated financial statements, we are required to make estimates and assumptions that affect the reported amounts and disclosures in our interim condensed consolidated financial statements. These estimates and assumptions are impacted by risks and uncertainties, including those associated with the Novel Coronavirus (COVID-19) pandemic that began in the first quarter of 2020. While we have made estimates and assumptions based on the facts and circumstances available as of the date of this report, the full impact of COVID-19 cannot be predicted, and actual results could differ materially from those estimates and assumptions. For further information, refer to the audited consolidated financial statements and notes included in our Annual Report on Form 10-K for the year ended December 31, 2019.
New Accounting Pronouncements and Other Regulatory Pronouncements, Policy [Policy Text Block]	Effect of New Accounting Standards and Other Regulatory Pronouncements Accounting Standard Update 2020-04 On March 12, 2020, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2020-04 - Reference Rate Reform (Topic 848) . This guidance provides optional expedients and exceptions that are intended to ease the burden of updating contracts to contain a new reference rate due to the discontinuation of the London Inter-Bank Offered Rate (LIBOR). This guidance is available immediately and may be implemented in any period prior to the guidance expiration on December 31, 2022. We are currently assessing which of our various contracts will require an update for a new reference rate and will determine the timing for our implementation of this guidance at the completion of that analysis. Accounting Standard Update 2019-12 On December 18, 2019, the FASB issued ASU 2019-12 - Income Taxes (Topic 740) . This guidance is intended to simplify the accounting and disclosure requirements for income taxes by removing various exceptions and requires that the effect of an enacted change in tax laws or rates be included in the annual effective tax rate computation in the interim period of the enactment. This guidance becomes effective at the beginning of our 2021 fiscal year. We expect to adopt this guidance on January 1, 2021 and we are currently assessing the impact that this standard will have on our consolidated financial statements. Accounting Standards Update 2016-13 On June 16, 2016, the FASB issued 2016-13 - Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . ASU 2016-13 replaces the incurred loss model under previous guidance, and requires entities to consider expected credit losses, in addition to past events and current conditions when measuring credit losses. This guidance applies to certain of our financial instruments and is primarily applicable to our trade accounts receivable. We adopted this guidance on January 1, 2020, using a modified-retrospective transition method and the adoption of this standard did not have a material impact on our condensed consolidated financial statements. See the Statement of Stockholders' Equity for the implementation impact of ASU 2016-13. Securities and Exchange Commission (SEC) Rule In the first quarter of 2020, the SEC adopted "Financial Disclosures about Guarantors and Issuers of Guaranteed Securities and Affiliates Whose Securities Collateralize a Registrant's Securities," a rule that amends the financial disclosure requirements for guarantors and issuers of registered guaranteed securities. This rule eliminates the previous requirement to present guarantor financial statement information in the notes to the financial statements and allows for the disclosure of summarized financial information for the most recent year and interim period, as well as expanded non-financial disclosures, in Management's Discussion and Analysis (MD&A). The effective date for this rule is January 4, 2021, however, the SEC permitted voluntary compliance prior to this date and we elected to adopt the new disclosure requirements in the first quarter of 2020. As such, we no longer present guarantor financial statement information in the notes to the condensed consolidated financial statements in this Quarterly Report on Form 10-Q, but instead present the required information within MD&A. Coronavirus Aid, Relief, and Economic Security Act The Coronavirus Aid, Relief, and Economic Security Act (the CARES Act) was enacted on March 27, 2020 in the United States. The key provisions of the CARES Act, as applicable to AAM, include the following: • The ability to use net operating losses (NOLs) to offset income without the 80% taxable income limitation enacted as part of the Tax Cuts and Jobs Act (TCJA) of 2017, and to carry back NOLs to offset prior year income for five years. These are temporary provisions that apply to NOLs incurred in 2018, 2019 or 2020 tax years. • The ability to claim a current deduction for interest expense up to 50% of Adjusted Taxable Income (ATI) for tax years 2019 and 2020. This limitation was previously 30% of ATI pursuant to the TCJA, and will revert to 30% after 2020. • The ability to defer the payment of the employer portion of social security taxes incurred between March 27, 2020 and December 31, 2020, with 50% of the deferred amount to be paid by December 31, 2021 and the remaining 50% to be paid by December 31, 2022.

Restructuring and Acquisition_2

Restructuring and Acquisition-Related Costs (Tables)	6 Months Ended
	Jun. 30, 2020
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs [Table Text Block]	A summary of our restructuring activity for the first six months of 2020 and 2019 is shown below: Severance Charges Implementation Costs Total (in millions) Accrual at December 31, 2018 $ 2.4 $ 1.6 $ 4.0 Charges 8.2 8.9 17.1 Cash utilization (7.9) (7.1) (15.0) Accrual at June 30, 2019 $ 2.7 $ 3.4 $ 6.1 Accrual at December 31, 2019 $ 4.8 $ 7.4 $ 12.2 Charges 16.3 7.7 24.0 Cash utilization (16.0) (8.9) (24.9) Accrual at June 30, 2020 $ 5.1 $ 6.2 $ 11.3
Business Combination, Separately Recognized Transactions [Table Text Block]	During the six months ended June 30, 2020 and 2019, we incurred the following integration charges primarily related to the integration of MPG: Integration Expenses (in millions) Charges for the six months ended June 30, 2020 $ 4.9 Charges for the six months ended June 30, 2019 7.2

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill [Table Text Block]	The following table provides a reconciliation of changes in goodwill for the six months ended June 30, 2020: Driveline Metal Forming Consolidated (in millions) Balance at December 31, 2019 $ 398.3 $ 300.8 $ 699.1 Impairment charge (210.8) (299.2) (510.0) Foreign currency translation (5.6) (1.6) (7.2) Balance at June 30, 2020 $ 181.9 $ — $ 181.9
Schedule of Finite-Lived Intangible Assets [Table Text Block]	The following table provides a reconciliation of the gross carrying amount and associated accumulated amortization for AAM's other intangible assets, which are all subject to amortization: June 30, December 31, 2020 2019 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount (in millions) Capitalized computer software $ 46.1 $ (30.8) $ 15.3 $ 45.8 $ (27.6) $ 18.2 Customer platforms 856.2 (206.1) 650.1 856.2 (174.4) 681.8 Customer relationships 53.0 (11.1) 41.9 53.0 (9.4) 43.6 Technology and other 156.0 (41.5) 114.5 156.0 (35.1) 120.9 Total $ 1,111.3 $ (289.5) $ 821.8 $ 1,111.0 $ (246.5) $ 864.5

Inventories (Tables)

Inventories (Tables)	6 Months Ended
	Jun. 30, 2020
Inventory Disclosure [Abstract]
Schedule of Inventory, Current [Table Text Block]	Inventories consist of the following: June 30, 2020 December 31, 2019 (in millions) Raw materials and work-in-progress $ 305.5 $ 310.4 Finished goods 81.1 83.7 Gross inventories 386.6 394.1 Inventory valuation reserves (28.1) (20.5) Inventories, net $ 358.5 $ 373.6

Long-Term Debt (Tables)

Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments [Table Text Block]	Long-term debt consists of the following: June 30, 2020 December 31, 2019 (in millions) Revolving Credit Facility $ 200.0 $ — Term Loan A Facility 340.0 340.0 Term Loan B Facility 1,188.8 1,188.8 6.875% Notes due 2028 400.0 — 6.625% Notes due 2022 350.0 450.0 6.50% Notes due 2027 500.0 500.0 6.25% Notes due 2026 400.0 400.0 6.25% Notes due 2025 700.0 700.0 Foreign credit facilities and other 109.6 113.4 Total debt 4,188.4 3,692.2 Less: Borrowings under Revolving Credit Facility 200.0 — Less: Current portion of long-term debt 373.7 28.7 Long-term debt 3,614.7 3,663.5 Less: Debt issuance costs 53.3 51.2 Long-term debt, net $ 3,561.4 $ 3,612.3

Derivatives (Tables)

Derivatives (Tables)	6 Months Ended
	Jun. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance [Table Text Block]	The following table summarizes the reclassification of derivative gains and losses into net income from accumulated other comprehensive income (loss) for those derivative instruments designated as cash flow hedges under ASC 815 - Derivatives and Hedging : Location Gain (Loss) Reclassified During Total of Financial Gain (Loss) Expected of Gain (Loss) Three Months Ended Six Months Ended Statement to be Reclassified Reclassified into June 30, June 30, Line Item During the Net Income 2020 2019 2020 2019 2020 Next 12 Months (in millions) Currency forward contracts Cost of Goods Sold $ (2.3) $ 0.7 $ (1.0) $ 0.9 $ 1,762.4 $ (5.8) Fixed-to-fixed cross-currency swap Other Income (Expense), net (3.7) — — — (2.2) 1.7 Variable-to-fixed interest rate swap Interest Expense (4.0) 0.7 (6.0) 1.9 (106.1) (16.2) See Note 12 - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (AOCI) for amounts recognized in other comprehensive income (loss) during the three and six months ended June 30, 2020 and 2019. The following table summarizes the amount and location of gains and losses recognized in the Condensed Consolidated Statements of Operations for those derivative instruments not designated as hedging instruments under ASC 815: Gain (Loss) Recognized During Total of Financial Location of Gain (Loss) Three Months Ended Six Months Ended Statement Line Recognized in June 30, June 30, Item Net Income 2020 2019 2020 2019 2020 (in millions) Currency forward contracts Cost of Goods Sold $ 0.8 $ 0.6 $ (7.6) $ 1.8 $ 1,762.4 Currency forward contracts Other Income (Expense), net (0.1) (0.4) (0.5) (0.6) (2.2)

Fair Value (Tables)

Fair Value (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	The estimated fair value of our financial assets and liabilities that are recognized at fair value on a recurring basis, using available market information and other observable data, are as follows: June 30, 2020 December 31, 2019 Carrying Amount Fair Value Carrying Amount Fair Value Input (in millions) Balance Sheet Classification Cash equivalents $ 745.1 $ 745.1 $ 271.3 $ 271.3 Level 1 Prepaid expenses and other Cash flow hedges - currency forward contracts — — 5.0 5.0 Level 2 Cash flow hedges - variable-to-fixed interest rate swap 6.0 6.0 0.9 0.9 Level 2 Nondesignated - currency forward contracts — — 1.9 1.9 Level 2 Other assets and deferred charges Cash flow hedges - currency forward contracts 0.3 0.3 3.4 3.4 Level 2 Cash flow hedges - fixed-to-fixed cross-currency swap 2.9 2.9 1.1 1.1 Level 2 Cash flow hedges - variable-to-fixed interest rate swap 12.1 12.1 2.2 2.2 Level 2 Accrued expenses and other Cash flow hedges - currency forward contracts 5.8 5.8 — — Level 2 Cash flow hedges - variable-to-fixed interest rate swap 20.0 20.0 7.9 7.9 Level 2 Nondesignated - currency forward contracts 3.1 3.1 — — Level 2 Postretirement benefits and other long-term liabilities Cash flow hedges - currency forward contracts 5.0 5.0 — — Level 2 Cash flow hedges - variable-to-fixed interest rate swap 41.1 41.1 18.4 18.4 Level 2
Fair Value, Financial Instruments not Carried at Fair Value [Table Text Block]	We estimated the fair value of the amounts outstanding on our debt using available market information and other observable data, to be as follows: June 30, 2020 December 31, 2019 Carrying Amount Fair Value Carrying Amount Fair Value Input (in millions) Revolving Credit Facility $ 200.0 $ 200.0 $ — $ — Level 2 Term Loan A Facility 340.0 312.0 340.0 337.9 Level 2 Term Loan B Facility 1,188.8 1,123.5 1,188.8 1,174.0 Level 2 6.875% Notes due 2028 400.0 394.0 — — Level 2 6.625% Notes due 2022 350.0 354.0 450.0 455.4 Level 2 6.50% Notes due 2027 500.0 482.5 500.0 516.3 Level 2 6.25% Notes due 2026 400.0 384.0 400.0 409.0 Level 2 6.25% Notes due 2025 700.0 673.8 700.0 716.6 Level 2

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	6 Months Ended
	Jun. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Schedule of Net Benefit (Credits) Costs [Table Text Block]	The components of net periodic benefit cost (credit) are as follows: Pension Benefits Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (in millions) Service cost $ 0.5 $ 0.4 $ 1.0 $ 0.7 Interest cost 5.4 7.1 10.8 14.2 Expected asset return (9.7) (10.3) (19.3) (20.6) Amortized loss 2.2 1.5 4.3 3.2 Net periodic benefit credit $ (1.6) $ (1.3) $ (3.2) $ (2.5) Other Postretirement Benefits Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (in millions) Service cost $ 0.1 $ 0.1 $ 0.2 $ 0.2 Interest cost 2.5 3.2 5.1 6.4 Amortized loss 0.3 — 0.5 0.1 Amortized prior service credit (0.4) (0.4) (0.8) (0.8) Net periodic benefit cost $ 2.5 $ 2.9 $ 5.0 $ 5.9

Product Warranties (Tables)

Product Warranties (Tables)	6 Months Ended
	Jun. 30, 2020
Product Warranties Disclosures [Abstract]
Schedule of Product Warranty Liability [Table Text Block]	The following table provides a reconciliation of changes in the product warranty liability: Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (in millions) Beginning balance $ 64.2 $ 56.2 $ 62.0 $ 57.7 Accruals 0.6 5.0 4.8 9.4 Payments (0.7) (3.6) (2.0) (7.3) Adjustment to prior period accruals (0.4) (2.0) (0.5) (4.3) Foreign currency translation 0.2 0.1 (0.4) 0.2 Ending balance $ 63.9 $ 55.7 $ 63.9 $ 55.7

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table sets forth the computation of our basic and diluted EPS available to shareholders of common stock (excluding participating securities): Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (in millions, except per share data) Numerator Net income (loss) attributable to AAM $ (213.2) $ 52.5 $ (714.5) $ 94.1 Less: Net income attributable to participating securities — (1.5) — (2.7) Net income (loss) attributable to common shareholders - Basic and Dilutive $ (213.2) $ 51.0 $ (714.5) $ 91.4 Denominators Basic common shares outstanding - Weighted-average shares outstanding 118.4 115.8 117.4 115.6 Less: Participating securities (5.3) (3.3) (4.5) (3.4) Weighted-average common shares outstanding 113.1 112.5 112.9 112.2 Effect of dilutive securities - Dilutive stock-based compensation — 0.3 — 0.4 Diluted shares outstanding - Adjusted weighted-average shares after assumed conversions 113.1 112.8 112.9 112.6 Basic EPS $ (1.88) $ 0.45 $ (6.33) $ 0.81 Diluted EPS $ (1.88) $ 0.45 $ (6.33) $ 0.81

Reclassifications out of Accu_2

Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 30, 2020
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Abstract]
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	Reclassification adjustments and other activity impacting accumulated other comprehensive income (loss) during the three months ended June 30, 2020 and June 30, 2019 are as follows (in millions) : Defined Benefit Plans Foreign Currency Translation Adjustments Unrecognized Gain (Loss) on Cash Flow Hedges Total Balance at March 31, 2020 $ (258.3) $ (149.7) $ (50.4) $ (458.4) Other comprehensive income (loss) before reclassifications — 4.8 (0.8) 4.0 Income tax effect of other comprehensive income (loss) before reclassifications — — 1.2 1.2 Amounts reclassified from accumulated other comprehensive loss 2.1 (a) — 10.0 (b) 12.1 Income taxes reclassified into net income (0.4) — (1.7) (2.1) Net change in accumulated other comprehensive loss 1.7 4.8 8.7 15.2 Balance at June 30, 2020 $ (256.6) $ (144.9) $ (41.7) $ (443.2) Defined Benefit Plans Foreign Currency Translation Adjustments Unrecognized Gain (Loss) on Cash Flow Hedges Total Balance at March 31, 2019 $ (240.9) $ (99.1) $ (3.6) $ (343.6) Other comprehensive income (loss) before reclassifications — 4.9 (19.1) (14.2) Income tax effect of other comprehensive income (loss) before reclassifications — — 4.6 4.6 Amounts reclassified from accumulated other comprehensive loss 1.3 (a) — (1.4) (b) (0.1) Income taxes reclassified into net income (0.2) — 0.1 (0.1) Net change in accumulated other comprehensive loss 1.1 4.9 (15.8) (9.8) Balance at June 30, 2019 $ (239.8) $ (94.2) $ (19.4) $ (353.4) (a) These amounts were reclassified from AOCI to Other income (expense), net for the three months ended June 30, 2020 and June 30, 2019. (b) The amounts reclassified from AOCI included $2.3 million in cost of goods sold (COGS), $4.0 million in interest expense and $3.7 million in Other income (expense), net for the three months ended June 30, 2020 and $(0.7) million in COGS and $(0.7) million in interest expense for the three months ended June 30, 2019. Reclassification adjustments and other activity impacting accumulated other comprehensive income (loss) during the six months ended June 30, 2020 and June 30, 2019 are as follows (in millions) : Defined Benefit Plans Foreign Currency Translation Adjustments Unrecognized Gain (Loss) on Cash Flow Hedges Total Balance at December 31, 2019 $ (259.9) $ (101.2) $ (15.7) $ (376.8) Other comprehensive income (loss) before reclassifications — (43.7) (34.8) (78.5) Income tax effect of other comprehensive income (loss) before reclassifications — — 3.1 3.1 Amounts reclassified from accumulated other comprehensive loss 4.1 (a) — 7.0 (b) 11.1 Income taxes reclassified into net income (0.8) — (1.3) (2.1) Net change in accumulated other comprehensive loss 3.3 (43.7) (26.0) (66.4) Balance at June 30, 2020 $ (256.6) $ (144.9) $ (41.7) $ (443.2) Defined Benefit Plans Foreign Currency Translation Adjustments Unrecognized Gain (Loss) on Cash Flow Hedges Total Balance at December 31, 2018 $ (213.9) $ (96.6) $ (1.1) $ (311.6) Other comprehensive income (loss) before reclassifications (27.9) (c) 2.4 (21.7) (47.2) Income tax effect of other comprehensive income (loss) before reclassifications — — 5.8 5.8 Amounts reclassified from accumulated other comprehensive income (loss) 2.5 (a) — (2.8) (b) (0.3) Income taxes reclassified into net income (0.5) — 0.4 (0.1) Net change in accumulated other comprehensive income (loss) (25.9) 2.4 (18.3) (41.8) Balance at June 30, 2019 $ (239.8) $ (94.2) $ (19.4) $ (353.4) (a) These amounts were reclassified from AOCI to Other income (expense), net for the six months ended June 30, 2020 and June 30, 2019. (b) The amounts reclassified from AOCI included $1.0 million in COGS and $6.0 million in interest expense for the six months ended June 30, 2020 and $(0.9) million in COGS and $(1.9) million in interest expense for the six months ended June 30, 2019. (c) ASU 2018-02 became effective on January 1, 2019, and we elected to reclassify the stranded tax effects caused by the 2017 Tax Cuts and Jobs Act, resulting in a decrease in Accumulated other comprehensive income (loss) of $27.7 million at January 1, 2019.

Disaggregation of Revenue (Tabl

Disaggregation of Revenue (Tables)	6 Months Ended
	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	Net sales recognized from contracts with customers, disaggregated by segment and geographical location, are presented in the following table for the three and six months ended June 30, 2020 and 2019. Net sales are attributed to regions based on the location of production. Intersegment sales have been excluded from the table. In the fourth quarter of 2019, we completed the sale of the U.S operations of our former Casting segment (the Casting Sale). The Casting Sale did not include the entities that conduct AAM's casting operations in El Carmen, Mexico, which are now included in our Driveline segment. The Casting Sale did not qualify for classification as discontinued operations, as it did not represent a strategic shift in our business that has had, or will have, a major effect on our operations and financial results. As such, we continue to present Casting as a segment in the table below for the three and six months ended June 30, 2019, and the reported amounts are now comprised entirely of the U.S. casting operations that were included in the sale. The amounts previously reported in our Casting segment for the retained operations in El Carmen, Mexico have been reclassified to our Driveline segment for the three and six months ended June 30, 2019. Three Months Ended June 30, 2020 Driveline Metal Forming Casting Total North America $ 260.4 $ 83.7 $ — $ 344.1 Asia 88.1 10.0 — 98.1 Europe 46.3 24.5 — 70.8 South America 1.7 0.6 — 2.3 Total $ 396.5 $ 118.8 $ — $ 515.3 Three Months Ended June 30, 2019 Driveline Metal Forming Casting Total North America $ 903.9 $ 301.4 $ 171.3 $ 1,376.6 Asia 135.0 7.9 — 142.9 Europe 90.8 67.2 — 158.0 South America 25.9 0.9 — 26.8 Total $ 1,155.6 $ 377.4 $ 171.3 $ 1,704.3 Six Months Ended June 30, 2020 Driveline Metal Forming Casting Total North America $ 1,051.7 $ 345.3 $ — $ 1,397.0 Asia 191.2 16.1 — 207.3 Europe 145.2 85.7 — 230.9 South America 20.4 3.2 — 23.6 Total $ 1,408.5 $ 450.3 $ — $ 1,858.8 Six Months Ended June 30, 2019 Driveline Metal Forming Casting Total North America $ 1,771.9 $ 606.8 $ 353.7 $ 2,732.4 Asia 288.3 15.4 — 303.7 Europe 192.4 139.9 — 332.3 South America 51.7 3.4 — 55.1 Total $ 2,304.3 $ 765.5 $ 353.7 $ 3,423.5 Contract Assets and Liabilities The following table summarizes our beginning and ending balances for accounts receivable and contract liabilities associated with our contracts with customers: Accounts Receivable, Net Contract Liabilities (Current) Contract Liabilities (Long-term) December 31, 2019 $ 815.4 $ 18.9 $ 83.7 June 30, 2020 550.2 22.5 78.5 Increase/(decrease) $ (265.2) $ 3.6 $ (5.2)

Segment Reporting (Tables)

Segment Reporting (Tables)	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment [Table Text Block]	The following tables represent information by reportable segment for the three months ended June 30, 2020 and 2019 (in millions) : Three Months Ended June 30, 2020 Driveline Metal Forming Casting Total Sales $ 403.7 $ 150.3 $ — $ 554.0 Less: intersegment sales 7.2 31.5 — 38.7 Net external sales $ 396.5 $ 118.8 $ — $ 515.3 Segment Adjusted EBITDA $ (31.2) $ (20.9) $ — $ (52.1) Three Months Ended June 30, 2019 Driveline Metal Forming Casting Total Sales $ 1,181.5 $ 484.2 $ 179.7 $ 1,845.4 Less: intersegment sales 25.9 106.8 8.4 141.1 Net external sales $ 1,155.6 $ 377.4 $ 171.3 $ 1,704.3 Segment Adjusted EBITDA $ 162.1 $ 86.5 $ 17.4 $ 266.0 The following tables represent information by reportable segment for the six months ended June 30, 2020 and 2019 (in millions) : Six Months Ended June 30, 2020 Driveline Metal Forming Casting Total Sales $ 1,435.4 $ 572.6 $ — $ 2,008.0 Less: intersegment sales 26.9 122.3 — 149.2 Net external sales $ 1,408.5 $ 450.3 $ — $ 1,858.8 Segment Adjusted EBITDA $ 108.1 $ 53.1 $ — $ 161.2 Six Months Ended June 30, 2019 Driveline Metal Forming Casting Total Sales $ 2,347.8 $ 967.5 $ 373.4 $ 3,688.7 Less: intersegment sales 43.5 202.0 19.7 265.2 Net external sales $ 2,304.3 $ 765.5 $ 353.7 $ 3,423.5 Segment Adjusted EBITDA $ 304.9 $ 170.9 $ 35.2 $ 511.0
Reconciliation of Total Segment Adjusted EBITDA to Income Before Income Taxes [Table Text Block]	The following table represents a reconciliation of Total Segment Adjusted EBITDA to consolidated income (loss) before income taxes for the three and six months ended June 30, 2020 and 2019 (in millions) : Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Total segment adjusted EBITDA $ (52.1) $ 266.0 $ 161.2 $ 511.0 Interest expense (54.6) (56.2) (106.1) (109.6) Depreciation and amortization (139.1) (136.5) (268.7) (277.3) Restructuring and acquisition-related costs (11.3) (12.2) (28.9) (24.3) Loss on sale of business — — (1.0) — Debt refinancing and redemption costs — (2.4) (1.5) (2.4) Impairment charge — — (510.0) — Income (loss) before income taxes $ (257.1) $ 58.7 $ (755.0) $ 97.4

Organization and Basis of Pre_3

Organization and Basis of Presentation (Details)	Jun. 30, 2020EmployeesCountriesFacilities
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Entity Number of Employees | Employees	20,000
Number of Facilities | Facilities	80
Number of Countries in which Entity Operates | Countries	17

Restructuring and Acquisition_3

Restructuring and Acquisition-Related Costs (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Restructuring Reserve [Roll Forward]
Restructuring reserve	$ 12.2	$ 4
Charges	24	17.1
Cash utilization	(24.9)	(15)
Restructuring reserve	11.3	6.1
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring reserve	4.8	2.4
Charges	16.3	8.2
Cash utilization	(16)	(7.9)
Restructuring reserve	5.1	2.7
Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring reserve	7.4	1.6
Charges	7.7	8.9
Cash utilization	(8.9)	(7.1)
Restructuring reserve	$ 6.2	$ 3.4

Restructuring Reserve Narrative

Restructuring Reserve Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 24	$ 17.1
Minimum [Member] | Forecast [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost			$ 70
Maximum [Member] | Forecast [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost			$ 80
Driveline [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	9.9	1.5
Metal Forming [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	10.4	9.8
Casting [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		0.7
2020 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	16.2
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	16.3	8.2
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 7.7	$ 8.9

Business Combinations, Separate

Business Combinations, Separately Recognized Transactions Table (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring and Related Activities [Abstract]
Integration expenses			$ 4.9	$ 7.2
Restructuring and acquisition-related costs	$ 11.3	$ 12.2	$ 28.9	$ 24.3

Goodwill Rollforward (Details)

Goodwill Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Goodwill [Roll Forward]
Goodwill			$ 699.1
Impairment charge	$ 0	$ 0	(510)	$ 0
Foreign currency translation			(7.2)
Goodwill	181.9		181.9
Driveline [Member]
Goodwill [Roll Forward]
Goodwill			398.3
Impairment charge			(210.8)
Foreign currency translation			(5.6)
Goodwill	181.9		181.9
Metal Forming [Member]
Goodwill [Roll Forward]
Goodwill			300.8
Impairment charge			(299.2)
Foreign currency translation			(1.6)
Goodwill	$ 0		$ 0

Goodwill Narrative (Details)

Goodwill Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Goodwill [Line Items]
Impairment charge	$ 0	$ 0	$ 510	$ 0
Goodwill, Impaired, Facts and Circumstances Leading to Impairment			These impairment charges were primarily the result of a decline in the projected cash flows of these reporting units under our revised long-range plan completed in the first quarter of 2020. The revision to our long-range plan was driven by lower forecasted sales volumes in the internal and external data sources used to form our projections primarily due to the reduction in global automotive production volumes caused by the impact of COVID-19. The impairment charges were also the result of changes in certain market-related inputs to the analysis to reflect macro-economic changes caused by the impact of COVID-19, including increased discount rates and lower pricing multiples for comparable public companies.
Goodwill, Impaired, Accumulated Impairment Loss	$ 1,435.5		$ 1,435.5
Driveline [Member]
Goodwill [Line Items]
Impairment charge			210.8
Metal Forming [Member]
Goodwill [Line Items]
Impairment charge			$ 299.2

Intangible Assets Table (Detail

Intangible Assets Table (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,111.3		$ 1,111.3		$ 1,111
Accumulated Amortization	(289.5)		(289.5)		(246.5)
Net Carrying Amount	821.8		821.8		864.5
Amortization of intangible assets	21.6	$ 24.9	43.4	$ 49.9
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Current Fiscal Year	80		80
Finite-Lived Intangible Assets, Amortization Expense, Year Two	80		80
Finite-Lived Intangible Assets, Amortization Expense, Year Three	80		80
Finite-Lived Intangible Assets, Amortization Expense, Year Four	80		80
Finite-Lived Intangible Assets, Amortization Expense, Year Five	80		80
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Current Fiscal Year	85		85
Finite-Lived Intangible Assets, Amortization Expense, Year Two	85		85
Finite-Lived Intangible Assets, Amortization Expense, Year Three	85		85
Finite-Lived Intangible Assets, Amortization Expense, Year Four	85		85
Finite-Lived Intangible Assets, Amortization Expense, Year Five	85		85
Computer Software, Intangible Asset [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	46.1		46.1		45.8
Accumulated Amortization	(30.8)		(30.8)		(27.6)
Net Carrying Amount	15.3		15.3		18.2
Customer Platforms - Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	856.2		856.2		856.2
Accumulated Amortization	(206.1)		(206.1)		(174.4)
Net Carrying Amount	650.1		650.1		681.8
Customer Relationships - Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	53		53		53
Accumulated Amortization	(11.1)		(11.1)		(9.4)
Net Carrying Amount	41.9		41.9		43.6
Technology-Based Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	156		156		156
Accumulated Amortization	(41.5)		(41.5)		(35.1)
Net Carrying Amount	$ 114.5		$ 114.5		$ 120.9

Inventories (Details)

Inventories (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Inventory [Line Items]
Raw materials and work-in-progress	$ 305.5	$ 310.4
Finished goods	81.1	83.7
Gross inventories	386.6	394.1
Inventory valuation reserves	(28.1)	(20.5)
Inventories, net	$ 358.5	$ 373.6

Schedule of Long-Term Debt (Det

Schedule of Long-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jul. 29, 2019	Apr. 06, 2017
Debt Instrument [Line Items]
Foreign credit facilities and other	$ 109.6	$ 113.4
Total debt	4,188.4	3,692.2
Borrowings under Revolving Credit Facility	200	0
Current portion of long-term debt	373.7	28.7
Long-term debt	3,614.7	3,663.5
Long-term debt, net	3,561.4	3,612.3
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding			$ 925	$ 932
Total Debt Instruments excluding Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Issuance Costs	53.3	51.2
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	200	0
Secured Debt [Member] | Term Loan A Due 2024 [Member]
Debt Instrument [Line Items]
Long-term Debt	340	340	$ 340
Secured Debt [Member] | Term Loan B [Member]
Debt Instrument [Line Items]
Long-term Debt	1,188.8	1,188.8
Unsecured Debt [Member] | 6.875% Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	400	0
Unsecured Debt [Member] | 6.625% Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	350	450
Unsecured Debt [Member] | 6.50% Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	500	500
Unsecured Debt [Member] | 6.25% Notes Due 2026 [Member]
Debt Instrument [Line Items]
Long-term Debt	400	400
Unsecured Debt [Member] | 6.25% Notes due 2025 [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 700	$ 700

Senior Secured Credit Facilitie

Senior Secured Credit Facilities Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jul. 29, 2019	Apr. 06, 2017
Debt Instrument [Line Items]
Payments of Debt Issuance Costs	$ 10.6	$ 0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit				$ 925	$ 932
Second Amendment to the Credit Agreement [Member]
Debt Instrument [Line Items]
Payments of Debt Issuance Costs	4.6
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	200		$ 0
Line of Credit Facility, Remaining Borrowing Capacity	691.4
Line of Credit Facility, Standby Letters of Credit Issued Against the Facility	33.6
Secured Debt [Member] | Term Loan B [Member]
Debt Instrument [Line Items]
Long-term Debt	1,188.8		1,188.8
Secured Debt [Member] | Term Loan A Due 2024 [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 340		$ 340	$ 340
AAM Inc. [Member] | Term Loan A [Member]
Debt Instrument [Line Items]
Long-term Debt					100
AAM Inc. [Member] | Term Loan B [Member]
Debt Instrument [Line Items]
Long-term Debt					1,550
AAM Inc. [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit					$ 932

Other Debt Disclosures Narrativ

Other Debt Disclosures Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Debt Instrument [Line Items]
Payments of Debt Issuance Costs			$ 10.6	$ 0
Long-term Debt, Weighted Average Interest Rate, at Point in Time			5.70%		5.80%
6.875% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			6.875%
6.625% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.625%	6.625%
Unsecured Debt [Member] | 6.875% Notes [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 400		$ 0
Payments of Debt Issuance Costs			6
Unsecured Debt [Member] | 6.625% Notes [Member]
Debt Instrument [Line Items]
Long-term Debt			350		450
Debt Instrument, Repurchase Amount		$ 100	350
Interest Paid, Including Capitalized Interest, Operating and Investing Activities		2
Write off of Deferred Debt Issuance Cost		0.4
Redemption Premium		$ 1.1
Unsecured Debt [Member] | 6.625% Notes [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchase Amount	$ 350
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	5.7
Write off of Deferred Debt Issuance Cost	1.3
Redemption Premium	$ 3.9
Foreign Credit Facilities [Member]
Debt Instrument [Line Items]
Long-term Line of Credit			109.6		$ 106
Debt Instrument, Unused Borrowing Capacity, Amount			$ 78.9

Derivatives Narrative (Details)

Derivatives Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 09, 2020
Foreign Currency Forward & Foreign Currency Option Contracts [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	$ 144.7
Currency Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	224.7
Fair value asset at date of dedesignation		$ 9.8
Interest Rate Swap [Member] | Debt [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Amount of Hedged Item, Through May 2021	900
Derivative, Amount of Hedged Item, Through May 2022	750
Derivative, Amount of Hedged Item, Through May 2023	600
Derivative, Amount of Hedged Item, Through May 2024	$ 500

Schedule of Derivatives (Detail

Schedule of Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Cost of goods sold	$ 614.2	$ 1,456	$ 1,762.4	$ 2,953
Other income (expense), net	0.1	(3.1)	(2.2)	(6.1)
Interest expense	(54.6)	(56.2)	$ (106.1)	(109.6)
Foreign Exchange Forward [Member] | Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Description of Location of Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments in Financial Statements			Cost of Goods Sold
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0.8	0.6	$ (7.6)	1.8
Foreign Exchange Forward [Member] | Cost of Sales [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Income Statement Location Gain (Loss) Reclassified from Accumulated OCI			Cost of Goods Sold
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(2.3)	0.7	$ (1)	0.9
Foreign Exchange Forward [Member] | Cost of Sales [Member] | Cash Flow Hedging [Member] | Forecast [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cash flow hedge gain (loss) to be reclassified within twelve months					$ (5.8)
Foreign Exchange Forward [Member] | Nonoperating Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Description of Location of Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments in Financial Statements			Other Income (Expense), net
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(0.1)	(0.4)	$ (0.5)	(0.6)
Currency Swap [Member] | Nonoperating Income (Expense) [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Income Statement Location Gain (Loss) Reclassified from Accumulated OCI			Other Income (Expense), net
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(3.7)	0	$ 0	0
Currency Swap [Member] | Nonoperating Income (Expense) [Member] | Cash Flow Hedging [Member] | Forecast [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cash flow hedge gain (loss) to be reclassified within twelve months					1.7
Interest Rate Swap [Member] | Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Income Statement Location Gain (Loss) Reclassified from Accumulated OCI			Interest Expense
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ (4)	$ 0.7	$ (6)	$ 1.9
Interest Rate Swap [Member] | Interest Expense [Member] | Cash Flow Hedging [Member] | Forecast [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cash flow hedge gain (loss) to be reclassified within twelve months					$ (16.2)

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value	$ 745.1	$ 271.3
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Fair Value	745.1	271.3
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Prepaid expenses and other [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	0	5
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Prepaid expenses and other [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	0	5
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	0.3	3.4
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	0.3	3.4
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Accrued expenses and other [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Liabilities, Fair Value Disclosure	5.8	0
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Accrued expenses and other [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Liabilities, Fair Value Disclosure	5.8	0
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Postretirement benefits and other long-term liabilities [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Liabilities, Fair Value Disclosure	5	0
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Postretirement benefits and other long-term liabilities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Liabilities, Fair Value Disclosure	5	0
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member] | Prepaid expenses and other [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	0	1.9
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member] | Prepaid expenses and other [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	0	1.9
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member] | Accrued expenses and other [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Liabilities, Fair Value Disclosure	3.1	0
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member] | Accrued expenses and other [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Liabilities, Fair Value Disclosure	3.1	0
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Prepaid expenses and other [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	6	0.9
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Prepaid expenses and other [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	6	0.9
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	12.1	2.2
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Assets, at Fair Value	12.1	2.2
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Accrued expenses and other [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	20	7.9
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Accrued expenses and other [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	20	7.9
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Postretirement benefits and other long-term liabilities [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	41.1	18.4
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Postretirement benefits and other long-term liabilities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	41.1	18.4
Currency Swap [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	2.9	1.1
Currency Swap [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Contract, Asset, Fair Value Disclosure	$ 2.9	$ 1.1

Fair Value of Debt (Details)

Fair Value of Debt (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jul. 29, 2019	Apr. 06, 2017
Revolving Credit Facility [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of Credit Facility, Amount Outstanding			$ 925	$ 932
Revolving Credit Facility [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of Credit Facility, Amount Outstanding	$ 200	$ 0
Revolving Credit Facility [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of Credit Facility, Amount Outstanding	200	0
Term Loan A Due 2024 [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	340	340
Term Loan A Due 2024 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	312	337.9
Term Loan B [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	1,188.8	1,188.8
Term Loan B [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	1,123.5	1,174
6.875% Notes [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	400	0
6.875% Notes [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	394	0
6.625% Notes [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	350	450
6.625% Notes [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	354	455.4
6.50% Notes [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	500	500
6.50% Notes [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	482.5	516.3
6.25% Notes Due 2026 [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	400	400
6.25% Notes Due 2026 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	384	409
6.25% Notes due 2025 [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	700	700
6.25% Notes due 2025 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	$ 673.8	$ 716.6

Schedule of Employee Benefit Pl

Schedule of Employee Benefit Plans Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 0.5	$ 0.4	$ 1	$ 0.7
Interest cost	5.4	7.1	10.8	14.2
Expected asset return	(9.7)	(10.3)	(19.3)	(20.6)
Amortized loss	2.2	1.5	4.3	3.2
Net periodic benefit credit	(1.6)	(1.3)	(3.2)	(2.5)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.1	0.1	0.2	0.2
Interest cost	2.5	3.2	5.1	6.4
Amortized loss	0.3	0	0.5	0.1
Amortized prior service credit	(0.4)	(0.4)	(0.8)	(0.8)
Net periodic benefit cost	$ 2.5	$ 2.9	$ 5	$ 5.9

Employee Benefit Plans and Othe

Employee Benefit Plans and Other Postretirement Benefit Plans Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Pension Plan, Noncurrent	$ 109.9	$ 118.2
Liability, Other Postretirement Defined Benefit Plan, Noncurrent	517.6	$ 520
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	1.5
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 17

Product Warranties (Details)

Product Warranties (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Product Warranty Rollforward
Beginning balance	$ 64.2	$ 56.2	$ 62	$ 57.7
Accruals	0.6	5	4.8	9.4
Payments	(0.7)	(3.6)	(2)	(7.3)
Adjustment to prior period accruals	(0.4)	(2)	(0.5)	(4.3)
Foreign currency translation	0.2	0.1	(0.4)	0.2
Ending balance	$ 63.9	$ 55.7	$ 63.9	$ 55.7

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Income tax expense (benefit)	$ (43.9)	$ 6	$ (40.6)	$ 3
Effective income tax rate, continuing operations	17.10%	10.20%	5.40%	3.10%
Tax Adjustments, Settlements, and Unusual Provisions	$ 18.5
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	25.3
Unrecognized tax benefit liability, including penalties and accrued interest	23.1		$ 23.1		$ 52.6
Settlement with Taxing Authority [Member]
Other Tax Expense (Benefit)	(6.8)
CARES Act [Member]
Other Tax Expense (Benefit)	(7)		$ (7.5)
Transition Tax [Member]
Other Tax Expense (Benefit)				$ (9.3)
UNITED STATES
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 36

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator
Net income (loss) attributable to AAM	$ (213.2)	$ 52.5	$ (714.5)	$ 94.1
Less: Net income attributable to participating securities	0	(1.5)	0	(2.7)
Net income (loss) attributable to common shareholders - Basic and Dilutive	$ (213.2)	$ 51	$ (714.5)	$ 91.4
Denominators
Basic - Weighted-average shares outstanding	118.4	115.8	117.4	115.6
Basic - Less: Participating securities	(5.3)	(3.3)	(4.5)	(3.4)
Basic - Weighted-average common shares outstanding	113.1	112.5	112.9	112.2
Effect of dilutive securities - dilutive stock-based compensation	0	0.3	0	0.4
Diluted - Adjusted weighted-average shares after assumed conversions	113.1	112.8	112.9	112.6
Basic EPS	$ (1.88)	$ 0.45	$ (6.33)	$ 0.81
Diluted EPS	$ (1.88)	$ 0.45	$ (6.33)	$ 0.81

Reclassifications out of Accu_3

Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), derivatives qualifying as hedges, tax	$ (0.5)		$ 4.7		$ 1.8	$ 6.2
Defined benefit plans, net current period other comprehensive income (loss)	1.7		1.1		3.3	1.8
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	4.8		4.9		(44)	2.4
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	8.7		(15.8)		(26)	(18.3)
Other comprehensive income (loss)	15.2		(9.8)		(66.7)	(14.1)
Accounting Standard Update 2018-02 [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
New accounting pronouncement, effect of adoption						27.7
Cost of Sales [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	2.3		(0.7)		1	(0.9)
Interest Expense [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	4		(0.7)		6	(1.9)
Other Income [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	3.7
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax - Beginning balance	(258.3)	$ (259.9)	(240.9)	$ (213.9)	(259.9)	(213.9)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	0		0		0	(27.9)
Income tax effect of other comprehensive income (loss) before reclassifications	0		0		0	0
Defined benefit plans, amounts reclassified from accumulated other comprehensive income (loss)	2.1		1.3		4.1	2.5
Income taxes reclassified into net income	(0.4)		(0.2)		(0.8)	(0.5)
Defined benefit plans, net current period other comprehensive income (loss)	1.7		1.1		3.3	(25.9)
Accumulated other comprehensive income (loss), net of tax - Ending balance	(256.6)	(258.3)	(239.8)	(240.9)	(256.6)	(239.8)
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax - Beginning balance	(149.7)	(101.2)	(99.1)	(96.6)	(101.2)	(96.6)
Foreign currency translation adjustments, other comprehensive income (loss) arising during period	4.8		4.9		(43.7)	2.4
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	0		0		0	0
Foreign currency translation adjustments, amounts reclassified from accumulated other comprehensive income (loss)	0		0		0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Tax	0		0		0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	4.8		4.9		(43.7)	2.4
Accumulated other comprehensive income (loss), net of tax - Ending balance	(144.9)	(149.7)	(94.2)	(99.1)	(144.9)	(94.2)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax - Beginning balance	(50.4)	(15.7)	(3.6)	(1.1)	(15.7)	(1.1)
Unrecognized gain (loss) on cash flow hedges, other comprehensive income (loss) arising during period	(0.8)		(19.1)		(34.8)	(21.7)
Other comprehensive income (loss), derivatives qualifying as hedges, tax	1.2		4.6		3.1	5.8
Unrecognized gain (loss) on cash flow hedges, amounts reclassified from accumulated other comprehensive income (loss)	10		(1.4)		7	(2.8)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	(1.7)		0.1		(1.3)	0.4
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	8.7		(15.8)		(26)	(18.3)
Accumulated other comprehensive income (loss), net of tax - Ending balance	(41.7)	(50.4)	(19.4)	(3.6)	(41.7)	(19.4)
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax - Beginning balance	(458.4)	(376.8)	(343.6)	(311.6)	(376.8)	(311.6)
Other comprehensive income (loss) arising during period, total	4		(14.2)		(78.5)	(47.2)
Other Comprehensive Income (Loss) before Reclassifications, Tax	1.2		4.6		3.1	5.8
Other comprehensive income (loss), reclassification before tax	12.1		(0.1)		11.1	(0.3)
Reclassification from AOCI, Current Period, Tax	(2.1)		(0.1)		(2.1)	(0.1)
Other comprehensive income (loss)	15.2		(9.8)		(66.4)	(41.8)
Accumulated other comprehensive income (loss), net of tax - Ending balance	$ (443.2)	$ (458.4)	$ (353.4)	$ (343.6)	$ (443.2)	$ (353.4)

Revenue from Contracts with C_2

Revenue from Contracts with Customers Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Net sales	$ 515.3	$ 1,704.3	$ 1,858.8	$ 3,423.5
North America [Member]
Disaggregation of Revenue [Line Items]
Net sales	344.1	1,376.6	1,397	2,732.4
Asia [Member]
Disaggregation of Revenue [Line Items]
Net sales	98.1	142.9	207.3	303.7
Europe [Member]
Disaggregation of Revenue [Line Items]
Net sales	70.8	158	230.9	332.3
South America [Member]
Disaggregation of Revenue [Line Items]
Net sales	2.3	26.8	23.6	55.1
Driveline [Member]
Disaggregation of Revenue [Line Items]
Net sales	396.5	1,155.6	1,408.5	2,304.3
Driveline [Member] | North America [Member]
Disaggregation of Revenue [Line Items]
Net sales	260.4	903.9	1,051.7	1,771.9
Driveline [Member] | Asia [Member]
Disaggregation of Revenue [Line Items]
Net sales	88.1	135	191.2	288.3
Driveline [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Net sales	46.3	90.8	145.2	192.4
Driveline [Member] | South America [Member]
Disaggregation of Revenue [Line Items]
Net sales	1.7	25.9	20.4	51.7
Metal Forming [Member]
Disaggregation of Revenue [Line Items]
Net sales	118.8	377.4	450.3	765.5
Metal Forming [Member] | North America [Member]
Disaggregation of Revenue [Line Items]
Net sales	83.7	301.4	345.3	606.8
Metal Forming [Member] | Asia [Member]
Disaggregation of Revenue [Line Items]
Net sales	10	7.9	16.1	15.4
Metal Forming [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Net sales	24.5	67.2	85.7	139.9
Metal Forming [Member] | South America [Member]
Disaggregation of Revenue [Line Items]
Net sales	0.6	0.9	3.2	3.4
Casting [Member]
Disaggregation of Revenue [Line Items]
Net sales	0	171.3	0	353.7
Casting [Member] | North America [Member]
Disaggregation of Revenue [Line Items]
Net sales	0	171.3	0	353.7
Casting [Member] | Asia [Member]
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Casting [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Net sales	0	0	0	0
Casting [Member] | South America [Member]
Disaggregation of Revenue [Line Items]
Net sales	$ 0	$ 0	$ 0	$ 0

Revenue from Contracts with C_3

Revenue from Contracts with Customers Contract Assets and Liabilities (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Accounts receivable, net	$ 550.2	$ 550.2	$ 815.4
Deferred revenue, current	22.5	22.5	18.9
Deferred revenue, noncurrent	78.5	78.5	$ 83.7
Increase (decrease) in accounts receivable		(265.2)
Contract liability, current, increase (decrease)		3.6
Contract liability, noncurrent, increase (decrease)		(5.2)
Contract with customer, liability, revenue recognized	$ 5.2	$ 11.9

Sales and Segment Adjusted EBIT

Sales and Segment Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Sales	$ 554	$ 1,845.4	$ 2,008	$ 3,688.7
Intersegment sales	38.7	141.1	149.2	265.2
Net external sales	515.3	1,704.3	1,858.8	3,423.5
Segment Adjusted EBITDA	(52.1)	266	161.2	511
Driveline [Member]
Segment Reporting Information [Line Items]
Sales	403.7	1,181.5	1,435.4	2,347.8
Intersegment sales	7.2	25.9	26.9	43.5
Net external sales	396.5	1,155.6	1,408.5	2,304.3
Segment Adjusted EBITDA	(31.2)	162.1	108.1	304.9
Metal Forming [Member]
Segment Reporting Information [Line Items]
Sales	150.3	484.2	572.6	967.5
Intersegment sales	31.5	106.8	122.3	202
Net external sales	118.8	377.4	450.3	765.5
Segment Adjusted EBITDA	(20.9)	86.5	53.1	170.9
Casting [Member]
Segment Reporting Information [Line Items]
Sales	0	179.7	0	373.4
Intersegment sales	0	8.4	0	19.7
Net external sales	0	171.3	0	353.7
Segment Adjusted EBITDA	$ 0	$ 17.4	$ 0	$ 35.2

Reconciliation of Total Segment

Reconciliation of Total Segment Adjusted EBITDA to Income Before Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Total segment adjusted EBITDA	$ (52.1)	$ 266	$ 161.2	$ 511
Interest expense	(54.6)	(56.2)	(106.1)	(109.6)
Depreciation and amortization	(139.1)	(136.5)	(268.7)	(277.3)
Restructuring and acquisition-related costs	(11.3)	(12.2)	(28.9)	(24.3)
Loss on sale of business	0	0	(1)	0
Debt refinancing and redemption costs	0	(2.4)	(1.5)	(2.4)
Impairment charge	0	0	(510)	0
Income (loss) before income taxes	$ (257.1)	$ 58.7	$ (755)	$ 97.4