Ally Financial (ALLY) 10-Q 31 Oct 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	9 Months Ended
	Sep. 30, 2017	Oct. 27, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Entity Registrant Name	Ally Financial Inc.
Entity Central Index Key	40,729
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		442,185,905
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 8,257,669,855

Condensed Consolidated Statemen

Condensed Consolidated Statement of Income Condensed Consolidated Statement of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Revenue and Other Income [Line Items]
Interest and Fee Income, Loans and Leases	$ 1,486	$ 1,307	$ 4,301	$ 3,807
Interest and Dividend Income, Securities, Operating, Available-for-sale	157	101	437	302
Interest Income, Deposits with Financial Institutions	11	3	23	10
Operating Leases, Income Statement, Lease Revenue	434	649	1,465	2,119
Total financing revenue and other interest income	2,088	2,060	6,226	6,238
Interest Expense [Abstract]
Interest Expense, Deposits	285	212	766	608
Interest Expense, Short-term Borrowings	34	14	94	39
Interest Expense, Long-term Debt	416	430	1,257	1,308
Interest Expense	735	656	2,117	1,955
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	272	408	982	1,352
Net Financing Revenue	1,081	996	3,127	2,931
Other revenue [Abstract]
Insurance Services Revenue	252	238	720	704
Gain (Loss) on Sales of Loans, Net	15	0	65	4
Gain (Loss) on Extinguishment of Debt	(4)	0	(6)	(4)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	23	52	73	145
Noninterest Income, Other Operating Income	95	98	313	289
Nonoperating Income (Expense)	381	388	1,165	1,138
Revenues	1,462	1,384	4,292	4,069
Provision for Loan Losses Expensed	314	258	854	650
Noninterest Expense [Abstract]
Labor and Related Expense	264	248	814	742
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	65	69	278	287
Other Noninterest Expense	424	418	1,249	1,189
Noninterest Expense	753	735	2,341	2,218
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	395	391	1,097	1,201
Income Tax Expense (Benefit)	115	130	350	336
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	280	261	747	865
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	2	(52)	1	(46)
Net Income (Loss) Attributable to Parent	282	209	748	819
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	48	(4)	144	262
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 330	$ 205	$ 892	$ 1,081
Earnings Per Share, Basic [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.62	$ 0.54	$ 1.63	$ 1.73
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	(0.11)	0	(0.10)
Earnings Per Share, Basic	0.63	0.43	1.63	1.63
Earnings Per Share, Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Diluted Share	0.62	0.54	1.63	1.72
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	(0.11)	0	(0.10)
Earnings Per Share, Diluted	0.63	0.43	1.63	1.63
Common Stock, Dividends, Per Share, Declared	$ 0.12	$ 0.08	$ 0.28	$ 0.08
Retained Earnings [Member]
Net Income (Loss) Attributable to Parent	$ 282	$ 209	$ 748	$ 819

Condensed Consolidated Balance

Condensed Consolidated Balance Sheet & Mini Balance Sheet - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Assets [Abstract]
Cash and Due from Banks	$ 810	$ 1,547
Interest-bearing Deposits in Banks and Other Financial Institutions	3,614	4,387
Cash and Cash Equivalents, at Carrying Value	4,424	5,934
Available-for-sale securities	23,099	18,926
Held-to-maturity securities	1,839	839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	18	0
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Gross	118,871	118,944
Financing Receivable, Allowance for Credit Losses	1,286	1,144
Loans and Leases Receivable, Net Amount	117,585	117,800
Property Subject to or Available for Operating Lease, Net	8,931	11,470
Premiums receivable and other insurance assets	2,054	1,905
Other Assets	6,063	6,854
Assets	164,013	163,728
Liabilities and Equity [Abstract]
Noninterest-bearing deposit liabilities	129	84
Interest-bearing Deposit Liabilities	89,987	78,938
Deposits	90,116	79,022
Short-term Debt	10,175	12,673
Long-term Debt	45,122	54,128
Interest payable	552	351
Unearned Premiums	2,583	2,500
Accounts Payable and Accrued Liabilities	1,892	1,737
Liabilities	150,440	150,411
Equity [Abstract]
Common Stocks, Including Additional Paid in Capital, Net of Discount	21,223	21,166
Retained Earnings (Accumulated Deficit)	(6,533)	(7,151)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(197)	(341)
Treasury stock, Value	(920)	(357)
Stockholders' Equity Attributable to Parent, Total	13,573	13,317
Liabilities and Equity	164,013	163,728
Variable Interest Entity, Primary Beneficiary [Member]
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Gross	20,020	24,630
Financing Receivable, Allowance for Credit Losses	134	173
Loans and Leases Receivable, Net Amount	19,886	24,457
Property Subject to or Available for Operating Lease, Net	704	1,745
Other Assets	1,037	1,390
Assets	21,627	27,592
Liabilities and Equity [Abstract]
Long-term Debt	10,046	13,259
Accounts Payable and Accrued Liabilities	10	12
Liabilities	$ 10,056	$ 13,271

Condensed Consolidated Balance4

Condensed Consolidated Balance Sheet and Mini Balance Sheet (Paranthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	1,100,000,000	1,100,000,000
Common Stock, Shares, Issued	489,593,314	485,707,644
Common Stock, Shares, Outstanding	443,796,233	467,000,306
Treasury Stock, Shares	45,797,081	18,707,338
Held-to-maturity Securities, Fair Value	$ 1,807	$ 789

Condensed Consolidated Stateme5

Condensed Consolidated Statement of Changes in Equity - USD ($) $ in Millions	Total	Common stock and paid-in capital [Member]	Preferred stock [Member]	Retained Earnings [Member]	Accumulated other comprehensive (loss) income [Member]	Treasury stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (231)				$ (231)
Stockholders' Equity Attributable to Parent at Dec. 31, 2015	13,439	$ 21,100	$ 696	$ (8,110)		$ (16)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	819			819
Dividends, Preferred Stock, Cash	(30)			(30)
Stock Repurchased During Period, Value	(696)		(696)
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	49	49
Other Comprehensive Income (Loss), Net of Tax	262				262
Treasury Stock, Value, Acquired, Cost Method	(173)					(173)
Dividends, Common Stock, Cash	(40)			(40)
Stockholders' Equity Attributable to Parent at Sep. 30, 2016	$ 13,630	21,149	0	(7,361)		(189)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.08
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 31				31
Accumulated Other Comprehensive Income (Loss), Net of Tax	(341)				(341)
Stockholders' Equity Attributable to Parent at Dec. 31, 2016	13,317	21,166	0	(7,151)		(357)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	748			748
Dividends, Preferred Stock, Cash	0
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	57	57
Other Comprehensive Income (Loss), Net of Tax	144				144
Treasury Stock, Value, Acquired, Cost Method	(563)					(563)
Dividends, Common Stock, Cash	(130)			(130)
Stockholders' Equity Attributable to Parent at Sep. 30, 2017	$ 13,573	$ 21,223	$ 0	$ (6,533)		$ (920)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.28
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (197)				$ (197)

Condensed Consolidated Stateme6

Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Income (Loss) Attributable to Parent	$ 748	$ 819
Depreciation, Amortization and Accretion, Net	1,434	1,807
Provision for Loan Losses Expensed Including Discontinued Operations	854	650
Gain Loss on Sales of Loans Net Including Discontinued Operations	65	4
Availableforsale Securities Gross Realized Gain Loss Excluding Otti Including Disc Ops	(73)	(145)
Gain (Loss) on Extinguishment of Debt	(6)	(4)
Payments for Origination and Purchases of Loans Held-for-sale	252	141
Proceeds from Sale of Loans Held-for-sale	236	184
Increase (Decrease) in Deferred Income Taxes	(289)	(322)
Increase (Decrease) in Interest Payable, Net	202	112
Increase (Decrease) in Other Operating Assets	57	(16)
Increase (Decrease) in Other Operating Liabilities	(19)	(65)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	(70)	(30)
Net Cash Provided by (Used in) Operating Activities	3,373	3,589
Net Cash (Used in) Provided by Investing Activities [Abstract]
Payments to Acquire Available-for-sale Securities	(9,022)	(11,027)
Proceeds from sales of available-for-sale securities	2,926	8,546
Proceeds from maturities and repayment of available-for-sale securities	2,002	2,411
Payments to Acquire Held-to-maturity Securities	(709)	(650)
Proceeds from Sale and Maturity of Held-to-maturity Securities	32	0
Payments for (Proceeds from) Loans and Leases	(3,125)	(2,924)
Proceeds from Sale of Loans Held-for-investment	1,323	4,221
Originations and repayments of loans held-for-investment and other	(1,021)	5,384
Purchases of operating lease assets	(2,844)	(2,360)
Disposals of operating lease assets	4,409	4,631
Payments to Acquire Interest in Subsidiaries and Affiliates	0	309
Increase (Decrease) in Restricted Cash	497	622
Increase (Decrease) in Non marketable equity securities	(20)	(401)
Payments for (Proceeds from) Other Investing Activities	(159)	(157)
Net cash provided by investing activities	(3,669)	(2,781)
Net Cash Used in Financing Activities [Abstract]
Proceeds from (Repayments of) Short-term Debt	(2,500)	(1,673)
Increase (Decrease) in Deposits	11,050	9,240
Proceeds from issuance of long-term debt	13,302	11,229
Repayments of long-term debt	(22,376)	(20,758)
Payments for Repurchase of Preferred Stock and Preference Stock	0	696
Payments for Repurchase of Common Stock	(563)	(173)
Payments of Dividends	(130)	(70)
Net cash (used in) provided by financing activities	(1,217)	(2,901)
Effect of exchange-rate changes on cash and cash equivalents	3	2
Cash and Cash Equivalents, Period Increase (Decrease)	(1,510)	(2,091)
Cash and Cash Equivalents, at Carrying Value	5,934	6,380
Cash and Cash Equivalents, at Carrying Value	4,424	4,289
Supplemental Cash Flow Information [Abstract]
Interest Paid	1,910	1,860
Income Taxes Paid	32	16
Held-to-maturity securities received in consideration for loans sold	56	0
Transfer of Portfolio Loans and Leases to Held-for-sale	1,326	4,231
Proceeds from sales and repayments of mortgage loans held-for-investment originally designated as held-for-sale	$ 29	$ 28

Description of Business, Basis

Description of Business, Basis of Presentation, and Changes in Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]	Description of Business, Basis of Presentation, and Changes in Significant Accounting Policies Ally Financial Inc. (together with its consolidated subsidiaries unless the context requires otherwise, Ally, the Company, or we, us, or our) is a leading digital financial services company and top 25 U.S. financial holding company (FHC) offering diversified financial products for consumers, businesses, automotive dealers, and corporate clients . Our legacy dates back to 1919, and Ally was redesigned in 2009 with a distinctive brand, innovative approach, and relentless focus on our customers. We reconverted to a Delaware corporation in 2009 and are registered as a bank holding company (BHC) under the Bank Holding Company Act of 1956 as amended and an FHC under the Gramm-Leach-Bliley Act of 1999 as amended . We are one of the largest full service automotive finance operations in the country with a deep expertise in automotive lending and a complementary automotive-focused insurance business. Our wholly-owned banking subsidiary, Ally Bank, has received numerous industry awards for its services and capabilities and is one of the largest and most respected online banks, uniquely positioned for the observed shifting trends in consumer and commercial banking preferences for digital banking . We offer a variety of deposit and banking products including CDs, online savings, money market and checking accounts, IRA products, a cash back credit card, and mortgage lending offerings through Ally Home. We have recently integrated a growing digital wealth management and online brokerage platform to enable consumers to have a variety of options in managing their savings and wealth. Additionally, through our corporate finance business, we offer lending solutions to middle-market companies. Our accounting and reporting policies conform to accounting principles generally accepted in the United States of America (GAAP). Additionally, where applicable, the policies conform to the accounting and reporting guidelines prescribed by bank regulatory authorities. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and that affect income and expenses during the reporting period and related disclosures. In developing the estimates and assumptions, management uses all available evidence; however, actual results could differ because of uncertainties associated with estimating the amounts, timing, and likelihood of possible outcomes. Our most significant estimates pertain to the allowance for loan losses, valuations of automotive lease assets and residuals, fair value of financial instruments, legal and regulatory reserves, and the determination of the provision for income taxes. The Condensed Consolidated Financial Statements at September 30, 2017 , and for the three months and nine months ended September 30, 2017 , and 2016 , are unaudited but reflect all adjustments that are, in management’s opinion, necessary for the fair presentation of the results for the interim periods presented. All such adjustments are of a normal recurring nature. These unaudited Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements (and the related Notes) included in our Annual Report on Form 10-K for the year ended December 31, 2016 , as filed on February 27, 2017, with the U.S. Securities and Exchange Commission (SEC). Significant Accounting Policies Income Taxes In calculating the provision for interim income taxes, in accordance with Accounting Standards Codification (ASC) 740, Income Taxes , we apply an estimated annual effective tax rate to year-to-date ordinary income. At the end of each interim period, we estimate the effective tax rate expected to be applicable for the full fiscal year. This method differs from that described in Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K, which describes our annual significant income tax accounting policy and related methodology. Securitizations and Variable Interest Entities We securitize, transfer, and service consumer and commercial automotive loans and operating leases. Securitization transactions typically involve the use of variable interest entities (VIEs) and are accounted for either as sales or secured borrowings. We may retain economic interests in securitized and sold assets, which are generally in the form of senior or subordinated interests, other residual interests, and servicing rights. In order to conclude whether or not a VIE is required to be consolidated, careful consideration and judgment must be given to our continuing involvement with the VIE. In circumstances where we have both the power to direct the activities of the entity that most significantly impact the entity's performance and the obligation to absorb losses or the right to receive benefits of the entity that could be significant, we would conclude that we are the primary beneficiary of the VIE, and would consolidate the entity. Consolidation of the VIE would also preclude us from recording an accounting sale on the transaction. In the case of a consolidated VIE, the accounting is consistent with a secured borrowing (e.g., we continue to carry the loans and we record the related securitized debt on our Condensed Consolidated Balance Sheet ). In transactions where we are not determined to be the primary beneficiary of the VIE, we must determine whether or not we achieve a sale for accounting purposes. In order to achieve a sale for accounting purposes, the assets being transferred must be legally isolated, not be constrained by restrictions from further transfer, and be deemed to be beyond our control. If we were to fail any of these three criteria for sale accounting, the transfer would be accounted for as a secured borrowing consistent with the preceding paragraph . Refer to Note 10 to the Condensed Consolidated Financial Statements for discussion on VIEs. Gains or losses on off-balance sheet securitizations take into consideration the fair value of any retained interests, including the value of certain servicing assets or liabilities, if any, which are initially recorded at fair value at the date of sale. The estimate of the fair value of the retained interests and servicing requires us to exercise significant judgment about the timing and amount of future cash flows from the interests. Refer to Note 21 to the Condensed Consolidated Financial Statements for a discussion of fair value estimates. Gains or losses on off-balance sheet securitizations and sales are reported in gain on mortgage and automotive loans, net, in our Condensed Consolidated Statement of Comprehensive Income . Retained interests are classified as securities or as other assets depending on their nature. On December 24, 2016, the risk retention rules under the Dodd-Frank Wall Street Reform and Consumer Protection Act (Dodd-Frank Act) of 2010 became effective, requiring us to retain at least five percent of the credit risk of the assets underlying asset-backed securitizations . This note was updated to address the Dodd-Frank Act risk retention rules and differs from our description in Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K. We retain servicing responsibilities for all of our consumer and commercial automotive loan and operating lease securitizations. We may receive servicing fees for off-balance sheet securitizations based on the securitized loan balances and certain ancillary fees, all of which are reported in servicing fees in the Condensed Consolidated Statement of Comprehensive Income. Typically, the fee we are paid for servicing consumer automotive finance receivables represents adequate compensation, and consequently, does not result in the recognition of a servicing asset or liability. Whether on- or off-balance sheet, the investors in the securitization trusts generally have no recourse to our assets outside of protections afforded through customary market representation and warranty repurchase provisions. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K regarding additional significant accounting policies. Recently Adopted Accounting Standards Stock Compensation — Improvements to Employee Share-Based Payment Accounting (ASU 2016-09) As of December 31, 2016, we adopted Accounting Standards Update (ASU) 2016-09. The amendments in this update changed several aspects of share-based payment accounting. The amendments allowed for an entity-wide accounting policy election to either account for forfeitures as they occur or estimate the number of awards that are expected to vest. We elected to account for forfeitures as they occur. The amendments modified the tax withholding requirements to allow entities to withhold an amount up to the employee’s maximum individual statutory tax rates without resulting in a liability classification of the award as opposed to limiting the withholding to the minimum statutory tax rates as required under previous accounting guidance. The amendments required that all excess tax benefits and tax deficiencies related to share-based payment awards be recognized in income tax expense or benefit in the income statement in the period in which they occur. The amendments also addressed the classification and presentation of certain items on the cash flow statement. Specifically, cash flows related to excess tax benefits should be classified as an operating activity instead of a financing activity and cash flows related to cash paid to a tax authority by an employer when withholding shares from an employee’s award for tax withholding purposes should be classified as a financing activity. The adoption of these amendments did not have a material impact to the financial statements. Recently Issued Accounting Standards Revenue from Contracts with Customers (ASU 2014-09) and Revenue from Contracts with Customers — Deferral of the Effective Date (ASU 2015-14) In May 2014, the Financial Accounting Standards Board (FASB) issued ASU 2014-09. The purpose of this guidance is to streamline and consolidate existing revenue recognition principles in GAAP and to converge revenue recognition principles with International Financial Reporting Standards (IFRS). The core principle of the amendments is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to receive in exchange for those goods or services. The amendments include a five step process for consideration of the core principle, guidance on the accounting treatment for costs associated with a contract, and disclosure requirements related to the revenue process. As originally issued, the amendments in ASU 2014-09 were to be effective beginning on January 1, 2017. However, in August 2015, the FASB issued ASU 2015-14, which deferred the effective date of the guidance until January 1, 2018, and permitted early adoption as of the original effective date in ASU 2014-09. The FASB has issued several additional ASUs to clarify guidance and provide implementation support for ASU 2014-09. Management has considered these additional ASUs when assessing the overall impact of ASU 2014-09. The amendments to the revenue recognition principles can be applied upon adoption either through a full retrospective application or on a modified retrospective basis with a cumulative effect adjustment on the date of initial adoption with certain practical expedients. Our implementation efforts to date related to this standard have included identifying revenue streams that are within the scope of this guidance, the evaluation of associated contracts and accounting policies, the evaluation of processes and systems of internal control, and the assessment of disclosure requirements of the standard. A majority of our revenue streams are not within the scope of this ASU as they are governed by other accounting standards. Management has determined that certain revenue streams and contractual arrangements are in scope of this guidance, including deposit fees, revenue on certain noninsurance contracts, brokering commissions through our insurance operations, sales of off-lease vehicles, remarketing fee income through SmartAuction, and commission and fee income generated through Ally Invest. Management does not expect these amendments to impact current revenue recognition patterns for a majority of the in scope revenue streams and contracts. However, we expect that the application of this guidance to noninsurance contracts within our insurance business will result in the deferral of certain amounts we currently recognize as revenue and expense upon the origination of the contract and the immediate recognition of certain expenses upon the origination of the contract that are currently deferred. Additionally, upon implementation we expect to expand our financial statement disclosures as required by the standard. Our assessment is not final; however, we do not expect the impact of the new guidance to these specific contracts to be material to the financial statements. We currently plan to adopt this guidance as of January 1, 2018, and expect to use the modified retrospective approach. Financial Instruments — Recognition and Measurement of Financial Assets (ASU 2016-01) In January 2016, the FASB issued ASU 2016-01. The amendments in this update modify the requirements related to the measurement of certain financial instruments in the statement of financial condition and results of operations. For equity investments (other than investments accounted for using the equity method), entities must measure such instruments at fair value with changes in fair value recognized in net income. Changes in fair value for equity securities will no longer be recognized through other comprehensive income. Reporting entities may continue to elect to measure equity investments that do not have a readily determinable fair value at cost with adjustments for impairment and observable changes in price. In addition, for a liability (other than a derivative liability) that an entity measures at fair value, any change in fair value related to the instrument-specific credit risk, that is the entity’s own-credit, should be presented separately in other comprehensive income and not as a component of net income. The amendments are effective on January 1, 2018, with early adoption permitted solely for the provisions pertaining to instrument-specific credit risk for liabilities measured at fair value. The amendments must be applied on a modified retrospective basis with a cumulative effect adjustment as of the beginning of the fiscal year of initial adoption. While the amendment requiring equity investments to be measured at fair value with changes in fair value recognized in net income will create additional volatility in our Condensed Consolidated Statement of Comprehensive Income , we do not anticipate the other amendments will have a material impact to our financial statements. We currently plan to adopt these amendments on January 1, 2018, and expect to use the modified retrospective approach as required. Leases (ASU 2016-02) In February 2016, the FASB issued ASU 2016-02. The amendments in this update primarily replace the existing accounting requirements for operating leases for lessees. Lessee accounting requirements for finance leases and lessor accounting requirements for operating leases and sales type and direct financing leases (sales type and direct financing leases were both previously referred to as capital leases) are largely unchanged. The amendments require the lessee of an operating lease to record a balance sheet gross-up upon lease commencement by recognizing a right-of-use asset and lease liability equal to the present value of the lease payments. The right-of-use asset and lease liability should be derecognized in a manner that effectively yields a straight line lease expense over the lease term. In addition to the changes to the lessee operating lease accounting requirements, the amendments also change the types of costs that can be capitalized related to a lease agreement for both lessees and lessors for all types of leases. The amendments also require additional disclosures for all lease types for both lessees and lessors. The amendments are effective on January 1, 2019, with early adoption permitted. The amendments must be applied on a modified retrospective basis with a cumulative adjustment to the beginning of the earliest fiscal year presented in the financial statements in the period of adoption. Management is currently evaluating the impact of these amendments. Upon adoption, we expect to record a balance sheet gross-up, reflecting our right-of-use asset and lease liability for our operating leases where we are the lessee (for example, our facility leases). We are currently reviewing our operating lease contracts where we are the lessee to determine the impact of the gross-up and the changes to capitalizable costs. We are also reviewing our leases where we are the lessor to determine the impact of the changes to capitalizable costs. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as required. Financial Instruments — Credit Losses (ASU 2016-13) In June 2016, the FASB issued ASU 2016-13. The amendments in this update introduce a new accounting model to measure credit losses for financial assets measured at amortized cost. Credit losses for financial assets measured at amortized cost should be determined based on the total current expected credit losses over the life of the financial asset or group of financial assets. In effect, the financial asset or group of financial assets should be presented at the net amount expected to be collected. Credit losses will no longer be measured as they are incurred for financial assets measured at amortized cost. The amendments also modify the accounting for available-for-sale debt securities whereby credit losses will be recorded through an allowance for credit losses rather than a write-down to the security’s cost basis, which allows for reversals of credit losses when estimated credit losses decline. Credit losses for available-for-sale debt securities should be measured in a manner similar to current GAAP. The amendments are effective on January 1, 2020, with early adoption permitted as of January 1, 2019. The amendments must be applied using a modified retrospective approach with a cumulative-effect adjustment through retained earnings as of the beginning of the fiscal year upon adoption. The new accounting model for credit losses represents a significant departure from existing GAAP, and will likely materially increase the allowance for credit losses with a resulting negative adjustment to retained earnings. Management created a formal working group to govern the implementation of these amendments consisting of key stakeholders from finance, risk, and accounting and is currently evaluating the impact of the amendments. We are in the process of designing and building the models and procedures that will be used to calculate the credit loss reserves in accordance with these amendments. We currently plan to adopt these amendments on January 1, 2020, and expect to use the modified retrospective approach as required. Statement of Cash Flows — Restricted Cash (ASU 2016-18) In November 2016, the FASB issued ASU 2016-18. The amendments in this update require that amounts classified as restricted cash and restricted cash equivalents be included within the beginning-of-period and end-of-period amounts along with cash and cash equivalents on the statement of cash flows. Prior to this ASU, specific guidance on the presentation of changes in restricted cash and restricted cash equivalents within the statement of cash flows did not exist. The amendments are effective on January 1, 2018, with early adoption permitted. The amendments must be applied retrospectively to all periods presented within the statement of cash flows upon adoption. The amendments will not impact financial results, but will result in a change in the presentation of restricted cash and restricted cash equivalents within the statement of cash flows. We currently plan to adopt these amendments on January 1, 2018, and expect to use the retrospective approach as required. Receivables — Nonrefundable Fees and Other Costs: Premium Amortization on Purchased Callable Debt Securities (ASU 2017-08) In March 2017, the FASB issued ASU 2017-08. The amendments in this update require premiums on purchased callable debt securities to be amortized to the security’s earliest call date. Prior to this ASU, premiums and discounts on purchased callable debt securities were generally required to be amortized to the security’s maturity date. The amendments do not require an accounting change for securities held at a discount. The amendments are effective on January 1, 2019, with early adoption permitted. The amendments must be applied using a modified retrospective approach with a cumulative-effect adjustment through retained earnings as of the beginning of the fiscal year upon adoption. Management is currently evaluating the impact of these amendments. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as required. Derivatives and Hedging — Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12) In August 2017, the FASB issued ASU 2017-12, which enhances the financial reporting of hedging relationships to better portray the economic results of an entity's risk management activities in its financial statements and make certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP. The amendments in this update better align an entity's risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and presentation of hedge results. The amendments are effective on January 1, 2019, with early adoption permitted. Entities must apply the amendments to cash flow and net investment hedge relationships that exist on the date of adoption using a modified retrospective approach. All transition requirements and elections must be applied to hedging relationships existing as of the adoption date and the effect of adoption should be reflected as of the beginning of the fiscal year of adoption. The presentation and disclosure requirements must be applied prospectively. We are currently evaluating the impact these amendments will have to our financial statements and are evaluating the potential of early adopting the standard on January 1, 2018.

Acquisitions Acquisitions

Acquisitions Acquisitions	9 Months Ended
	Sep. 30, 2017
Acquisitions [Abstract]
Business Combination Disclosure [Text Block]	Acquisitions On June 1, 2016 , we acquired 100% of the equity of TradeKing Group, Inc. (TradeKing), a digital wealth management company with an online broker-dealer, digital portfolio management platform, and educational content for $298 million in cash. TradeKing, which has been rebranded as Ally Invest, operates as a wholly-owned subsidiary of Ally Financial Inc. The addition of brokerage and wealth management is a natural extension of our online banking franchise, creating a full suite of financial products for savings and investments. We applied the acquisition method of accounting to this transaction, which generally requires the initial recognition of assets acquired, including identifiable intangible assets, and liabilities assumed at their respective fair value. Goodwill is recognized as the excess of the acquisition price after the recognition of the net assets, including the identifiable intangible assets. Beginning in June 2016, financial information related to Ally Invest is included within Corporate and Other. The following table summarizes the allocation of cash consideration paid for TradeKing and the amounts of the identifiable assets acquired and liabilities assumed recognized at the acquisition date. ($ in millions) Purchase price Cash consideration $ 298 Allocation of purchase price to net assets acquired Intangible assets (a) 82 Cash and short-term investments (b) 50 Other assets 14 Deferred tax asset, net 4 Employee compensation and benefits (41 ) Other liabilities (4 ) Goodwill $ 193 (a) We recorded $3 million and $8 million of amortization on these intangible assets during the three months and nine months ended September 30, 2017 , respectively, and $3 million during both the three months and nine months ended September 30, 2016 . (b) Includes $40 million in cash proceeds from the acquisition transaction in order to pay employee compensation and benefits that vested upon acquisition as a result of the change in control. The goodwill of $193 million arising from the acquisition consists largely of expected growth of the business as we leverage the Ally brand and our marketing capabilities to scale the acquired technology platform and expand the suite of financial products we offer to our existing growing customer base. None of the goodwill recognized is expected to be deductible for income tax purposes. Refer to Note 12 for the carrying amount of goodwill at the beginning and end of the reporting period. On August 1, 2016, we acquired assets that constitute a business from Blue Yield, an online automotive lender exchange which we rebranded as Clearlane, as we continue to expand our automotive finance offerings to include a direct-to-consumer option. We completed the acquisition for $28 million of total consideration. As a result of the purchase, we recognized $20 million of goodwill within Automotive Finance operations.

Discontinued Operations

Discontinued Operations	9 Months Ended
	Sep. 30, 2017
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	Discontinued Operations Prior to the adoption of ASU 2014-08, which was prospectively applied only to newly identified disposals that qualify as discontinued operations beginning after January 1, 2015, we have classified operations as discontinued when operations and cash flows will be eliminated from our ongoing operations and we do not expect to retain any significant continuing involvement in their operations after the respective sale or disposal transactions. For all periods presented, the operating results for these discontinued operations have been removed from continuing operations and presented separately as discontinued operations, net of tax, in the Condensed Consolidated Statement of Comprehensive Income . The Notes to the Condensed Consolidated Financial Statements have been adjusted to exclude discontinued operations unless otherwise noted. Our discontinued operations relate to previous discontinued operations in our Automotive Finance operations, Insurance operations, and Corporate Finance operating segments, and other operations for which we continue to have wind-down, legal, and minimal operational costs. Select financial information of discontinued operations is summarized below. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Pretax loss $ (1 ) $ (46 ) $ (2 ) $ (44 ) Tax (benefit) expense (3 ) 6 (3 ) 2

Other Income, Net of Losses

Other Income, Net of Losses	9 Months Ended
	Sep. 30, 2017
Other Nonoperating Income (Expense) [Abstract]
Other Income and Other Expense Disclosure [Text Block]	Other Income, Net of Losses Details of other income, net of losses, were as follows. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Remarketing fees $ 26 $ 26 $ 82 $ 79 Late charges and other administrative fees 25 25 77 72 Servicing fees 11 18 41 49 Income from equity-method investments 7 3 12 14 Other, net 26 26 101 75 Total other income, net of losses $ 95 $ 98 $ 313 $ 289

Reserves for Insurance Losses a

Reserves for Insurance Losses and Loss Adjustment Expenses Reserves for Insurance Losses and Loss Adjustment Expenses	9 Months Ended
	Sep. 30, 2017
Reserves for Insurance Losses and Loss Adjustment Expenses [Abstract]
Short-Duration Insurance and Deposit Contracts [Text Block]	Reserves for Insurance Losses and Loss Adjustment Expenses The following table shows a rollforward of our reserves for insurance losses and loss adjustment expenses. ($ in millions) 2017 2016 Total gross reserves for insurance losses and loss adjustment expenses at January 1, $ 149 $ 169 Less: Reinsurance recoverable 108 120 Net reserves for insurance losses and loss adjustment expenses at January 1, 41 49 Net insurance losses and loss adjustment expenses incurred related to: Current year 276 291 Prior years (a) 2 (4 ) Total net insurance losses and loss adjustment expenses incurred 278 287 Net insurance losses and loss adjustment expenses paid or payable related to: Current year (248 ) (266 ) Prior years (31 ) (27 ) Total net insurance losses and loss adjustment expenses paid or payable (279 ) (293 ) Foreign exchange and other 1 1 Net reserves for insurance losses and loss adjustment expenses at September 30, 41 44 Plus: Reinsurance recoverable 132 106 Total gross reserves for insurance losses and loss adjustment expenses at September 30, $ 173 $ 150 (a) There have been no material adverse changes to the reserve for prior years.

Other Operating Expenses

Other Operating Expenses	9 Months Ended
	Sep. 30, 2017
Operating Expenses [Abstract]
Other Operating Income and Expense [Text Block]	Other Operating Expenses Details of other operating expenses were as follows. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Insurance commissions $ 106 $ 99 $ 309 $ 290 Technology and communications 72 70 212 203 Lease and loan administration 41 34 116 100 Advertising and marketing 33 27 96 75 Vehicle remarketing and repossession 29 24 82 70 Regulatory and licensing fees 27 26 82 68 Professional services 28 25 81 75 Premises and equipment depreciation 22 19 67 61 Occupancy 11 13 34 38 Non-income taxes 6 10 22 27 Other 49 71 148 182 Total other operating expenses $ 424 $ 418 $ 1,249 $ 1,189

Investment Securities

Investment Securities	9 Months Ended
	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]	Investment Securities Our portfolio of securities includes bonds, equity securities, asset-backed securities, commercial and residential mortgage-backed securities, and other investments. The cost, fair value, and gross unrealized gains and losses on investment securities were as follows. September 30, 2017 December 31, 2016 Amortized cost Gross unrealized Fair value Amortized cost Gross unrealized Fair ($ in millions) gains losses gains losses Available-for-sale securities Debt securities U.S. Treasury (a) $ 2,112 $ — $ (39 ) $ 2,073 $ 1,680 $ — $ (60 ) $ 1,620 U.S. States and political subdivisions 849 12 (10 ) 851 794 7 (19 ) 782 Foreign government 157 2 (2 ) 157 157 5 — 162 Agency mortgage-backed residential 14,423 54 (133 ) 14,344 10,473 29 (212 ) 10,290 Mortgage-backed residential 2,326 16 (32 ) 2,310 2,162 5 (70 ) 2,097 Mortgage-backed commercial 509 2 (2 ) 509 537 2 (2 ) 537 Asset-backed 1,036 4 (1 ) 1,039 1,396 6 (2 ) 1,400 Corporate debt 1,291 10 (10 ) 1,291 1,452 7 (16 ) 1,443 Total debt securities (b) (c) 22,703 100 (229 ) 22,574 18,651 61 (381 ) 18,331 Equity securities 563 12 (50 ) 525 642 7 (54 ) 595 Total available-for-sale securities $ 23,266 $ 112 $ (279 ) $ 23,099 $ 19,293 $ 68 $ (435 ) $ 18,926 Held-to-maturity securities Debt securities Agency mortgage-backed residential (d) $ 1,799 $ 4 $ (36 ) $ 1,767 $ 839 $ — $ (50 ) $ 789 Asset-backed retained notes 40 — — 40 — — — — Total held-to-maturity securities $ 1,839 $ 4 $ (36 ) $ 1,807 $ 839 $ — $ (50 ) $ 789 (a) Includes $304 million of U.S. Treasury securities that are included in a fair value hedging relationship as of September 30, 2017. Refer to Note 19 for additional information. (b) Certain entities related to our Insurance operations are required to deposit securities with state regulatory authorities. These deposited securities totaled $12 million and $14 million at September 30, 2017 , and December 31, 2016 , respectively. (c) Investment securities with a fair value of $6,705 million and $4,881 million at September 30, 2017 , and December 31, 2016 , respectively, were pledged to secure advances from the Federal Home Loan Bank (FHLB), short-term borrowings or repurchase agreements, or for other purposes as required by contractual obligation or law. Under these agreements, we have granted the counterparty the right to sell or pledge $1,339 million and $737 million of the underlying investment securities at September 30, 2017 , and December 31, 2016 , respectively. (d) Agency mortgage-backed residential debt securities are held for liquidity risk management purposes. Securities with a fair value of $115 million and $87 million at September 30, 2017 , and December 31, 2016 , respectively, were pledged to secure advances from the FHLB. The maturity distribution of investment securities outstanding is summarized in the following tables. Call or prepayment options may cause actual maturities to differ from contractual maturities. Total Due in one year or less Due after one year through five years Due after five years through ten years Due after ten years ($ in millions) Amount Yield Amount Yield Amount Yield Amount Yield Amount Yield September 30, 2017 Fair value of available-for-sale debt securities (a) U.S. Treasury $ 2,073 1.8 % $ — — % $ 467 1.7 % $ 1,606 1.8 % $ — — % U.S. States and political subdivisions 851 2.9 69 1.6 35 2.4 197 2.7 550 3.2 Foreign government 157 2.5 — — 69 2.6 88 2.4 — — Agency mortgage-backed residential 14,344 3.1 — — — — 3 2.9 14,341 3.1 Mortgage-backed residential 2,310 3.0 — — — — — — 2,310 3.0 Mortgage-backed commercial 509 3.1 — — — — 31 2.9 478 3.1 Asset-backed 1,039 3.0 2 1.6 762 3.1 137 3.1 138 2.7 Corporate debt 1,291 2.9 135 2.5 595 2.6 515 3.2 46 4.9 Total available-for-sale debt securities $ 22,574 2.9 $ 206 2.2 $ 1,928 2.6 $ 2,577 2.2 $ 17,863 3.1 Amortized cost of available-for-sale debt securities $ 22,703 $ 206 $ 1,929 $ 2,609 $ 17,959 Amortized cost of held-to-maturity securities Agency mortgage-backed residential $ 1,799 3.1 % $ — — % $ — — % $ — — % $ 1,799 3.1 % Asset-backed retained notes 40 1.7 — — 39 1.6 1 3.0 — — Total held-to-maturity securities $ 1,839 3.1 $ — — $ 39 1.6 $ 1 3.0 $ 1,799 3.1 December 31, 2016 Fair value of available-for-sale debt securities (a) U.S. Treasury $ 1,620 1.7 % $ 2 4.6 % $ 60 1.6 % $ 1,558 1.7 % $ — — % U.S. States and political subdivisions 782 3.1 64 1.7 29 2.3 172 2.8 517 3.4 Foreign government 162 2.6 — — 58 2.8 104 2.4 — — Agency mortgage-backed residential 10,290 2.9 — — — — 29 2.6 10,261 2.9 Mortgage-backed residential 2,097 2.9 — — — — — — 2,097 2.9 Mortgage-backed commercial 537 2.6 — — — — 3 2.8 534 2.6 Asset-backed 1,400 2.8 — — 1,059 2.8 143 3.2 198 2.6 Corporate debt 1,443 2.8 72 2.2 840 2.6 489 3.2 42 4.7 Total available-for-sale debt securities $ 18,331 2.8 $ 138 2.0 $ 2,046 2.7 $ 2,498 2.2 $ 13,649 2.9 Amortized cost of available-for-sale debt securities $ 18,651 $ 138 $ 2,040 $ 2,563 $ 13,910 Amortized cost of held-to-maturity securities (b) $ 839 2.9 % $ — — % $ — — % $ — — % $ 839 2.9 % (a) Yield is calculated using the effective yield of each security at the end of the period, weighted based on the market value. The effective yield considers the contractual coupon and amortized cost, and excludes expected capital gains and losses. (b) Our held-to-maturity securities portfolio as of December 31, 2016, consisted of agency mortgage-backed residential debt securities. The balances of cash equivalents were $304 million and $291 million at September 30, 2017 , and December 31, 2016 , respectively, and were composed primarily of money market accounts and short-term securities, including U.S. Treasury bills. The following table presents interest and dividends on investment securities. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Taxable interest $ 141 $ 93 $ 390 $ 276 Taxable dividends 3 4 8 13 Interest and dividends exempt from U.S. federal income tax 6 4 17 13 Interest and dividends on investment securities $ 150 $ 101 $ 415 $ 302 The following table presents gross gains and losses realized upon the sales of available-for-sale securities. There were no other-than-temporary impairments upon the sales of available-for-sale securities for either period. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Gross realized gains $ 24 $ 52 $ 75 $ 146 Gross realized losses (a) (1 ) — (2 ) (1 ) Other gain on investments, net $ 23 $ 52 $ 73 $ 145 (a) Certain available-for-sale securities were sold at a loss in 2017 and 2016 as a result of market conditions within these respective periods (e.g., a downgrade in the rating of a debt security). Any such sales were made in accordance with our risk management policies and practices. The table below summarizes available-for-sale securities in an unrealized loss position in accumulated other comprehensive income. Based on the assessment of whether such losses were deemed to be other-than-temporary, we believe that the unrealized losses are not indicative of an other-than-temporary impairment of these securities. As of September 30, 2017 , we did not have the intent to sell the debt securities with an unrealized loss position in accumulated other comprehensive income, it is not more likely than not that we will be required to sell these securities before recovery of their amortized cost basis, and we expect to recover the entire amortized cost basis of the securities. As of September 30, 2017 , we had the ability and intent to hold equity securities with an unrealized loss position in accumulated other comprehensive income, and it is not more likely than not that we will be required to sell these securities before recovery of their amortized cost basis. As a result, we believe that the securities with an unrealized loss position in accumulated other comprehensive income are not considered to be other-than-temporarily impaired at September 30, 2017 . Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for additional information related to investment securities and our methodology for evaluating potential other-than-temporary impairments. September 30, 2017 December 31, 2016 Less than 12 months 12 months or longer Less than 12 months 12 months or longer ($ in millions) Fair value Unrealized loss Fair value Unrealized loss Fair value Unrealized loss Fair value Unrealized loss Available-for-sale securities Debt securities U.S. Treasury $ 2,029 $ (39 ) $ — $ — $ 1,612 $ (60 ) $ — $ — U.S. States and political subdivisions 311 (4 ) 138 (6 ) 524 (19 ) — — Foreign government 78 (2 ) — — 38 — — — Agency mortgage-backed residential 7,444 (115 ) 730 (18 ) 8,052 (196 ) 587 (16 ) Mortgage-backed residential 103 (1 ) 825 (31 ) 813 (17 ) 860 (53 ) Mortgage-backed commercial 164 (2 ) 15 — 47 (1 ) 149 (1 ) Asset-backed 341 (1 ) 86 — 375 (2 ) 127 — Corporate debt 388 (6 ) 108 (4 ) 744 (14 ) 46 (2 ) Total temporarily impaired debt securities 10,858 (170 ) 1,902 (59 ) 12,205 (309 ) 1,769 (72 ) Temporarily impaired equity securities 101 (8 ) 119 (42 ) 151 (8 ) 269 (46 ) Total temporarily impaired available-for-sale securities $ 10,959 $ (178 ) $ 2,021 $ (101 ) $ 12,356 $ (317 ) $ 2,038 $ (118 )

Finance Receivables and Loans,

Finance Receivables and Loans, Net	9 Months Ended
	Sep. 30, 2017
Loans and Leases Receivable, Net Amount [Abstract]
Loans, Notes, Trade and Other Receivables Disclosure [Text Block]	Finance Receivables and Loans, Net The composition of finance receivables and loans reported at gross carrying value was as follows. ($ in millions) September 30, 2017 December 31, 2016 Consumer automotive (a) $ 67,077 $ 65,793 Consumer mortgage Mortgage Finance (b) 9,760 8,294 Mortgage — Legacy (c) 2,255 2,756 Total consumer mortgage 12,015 11,050 Total consumer 79,092 76,843 Commercial Commercial and industrial Automotive 31,985 35,041 Other 3,774 3,248 Commercial real estate — Automotive 4,020 3,812 Total commercial 39,779 42,101 Total finance receivables and loans (d) $ 118,871 $ 118,944 (a) Includes $24 million and $43 million of fair value adjustment for loans in hedge accounting relationships at September 30, 2017 , and December 31, 2016 , respectively. Refer to Note 19 for additional information. (b) Includes loans originated as interest-only mortgage loans of $24 million and $30 million at September 30, 2017 , and December 31, 2016 , respectively, 35% of which are expected to start principal amortization in 2019 , and 44% in 2020 . The remainder of these loans have already exited the interest-only period. (c) Includes loans originated as interest-only mortgage loans of $538 million and $714 million at September 30, 2017 , and December 31, 2016 , respectively, 2% of which are expected to start principal amortization in 2018 , and 1% beyond 2020. The remainder of these loans have already exited the interest-only period. (d) Totals include net increases of $494 million and $359 million at September 30, 2017 , and December 31, 2016 , respectively, for unearned income, unamortized premiums and discounts, and deferred fees and costs. The following tables present an analysis of the activity in the allowance for loan losses on finance receivables and loans. Three months ended September 30, 2017 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at July 1, 2017 $ 1,002 $ 83 $ 140 $ 1,225 Charge-offs (a) (327 ) (7 ) (10 ) (344 ) Recoveries 85 6 — 91 Net charge-offs (242 ) (1 ) (10 ) (253 ) Provision for loan losses 314 — — 314 Other — (1 ) 1 — Allowance at September 30, 2017 $ 1,074 $ 81 $ 131 $ 1,286 (a) Represents the amount of the gross carrying value directly written off. For consumer and commercial loans, the loss from a charge-off is measured as the difference between the gross carrying value of a loan and the fair value of the collateral, less costs to sell. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for more information regarding our charge-off policies. Three months ended September 30, 2016 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at July 1, 2016 $ 862 $ 109 $ 118 $ 1,089 Charge-offs (a) (293 ) (10 ) — (303 ) Recoveries 74 16 — 90 Net charge-offs (219 ) 6 — (213 ) Provision for loan losses 269 (15 ) 4 258 Allowance at September 30, 2016 $ 912 $ 100 $ 122 $ 1,134 (a) Represents the amount of the gross carrying value directly written off. For consumer and commercial loans, the loss from a charge-off is measured as the difference between the gross carrying value of a loan and the fair value of the collateral, less costs to sell. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for more information regarding our charge-off policies. Nine months ended September 30, 2017 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at January 1, 2017 $ 932 $ 91 $ 121 $ 1,144 Charge-offs (a) (958 ) (22 ) (10 ) (990 ) Recoveries 266 19 — 285 Net charge-offs (692 ) (3 ) (10 ) (705 ) Provision for loan losses 841 (6 ) 19 854 Other (b) (7 ) (1 ) 1 (7 ) Allowance at September 30, 2017 $ 1,074 $ 81 $ 131 $ 1,286 Allowance for loan losses at September 30, 2017 Individually evaluated for impairment $ 35 $ 30 $ 21 $ 86 Collectively evaluated for impairment 1,039 51 110 1,200 Finance receivables and loans at gross carrying value Ending balance $ 67,077 $ 12,015 $ 39,779 $ 118,871 Individually evaluated for impairment 403 237 146 786 Collectively evaluated for impairment 66,674 11,778 39,633 118,085 (a) Represents the amount of the gross carrying value directly written off. For consumer and commercial loans, the loss from a charge-off is measured as the difference between the gross carrying value of a loan and the fair value of the collateral, less costs to sell. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for more information regarding our charge-off policies. (b) Primarily related to the transfer of finance receivables and loans from held-for-investment to held-for-sale. Nine months ended September 30, 2016 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at January 1, 2016 $ 834 $ 114 $ 106 $ 1,054 Charge-offs (a) (773 ) (29 ) (1 ) (803 ) Recoveries 233 25 1 259 Net charge-offs (540 ) (4 ) — (544 ) Provision for loan losses 644 (10 ) 16 650 Other (b) (26 ) — — (26 ) Allowance at September 30, 2016 $ 912 $ 100 $ 122 $ 1,134 Allowance for loan losses at September 30, 2016 Individually evaluated for impairment $ 24 $ 35 $ 25 $ 84 Collectively evaluated for impairment 888 65 97 1,050 Finance receivables and loans at gross carrying value Ending balance $ 64,816 $ 10,857 $ 39,286 $ 114,959 Individually evaluated for impairment 349 251 111 711 Collectively evaluated for impairment 64,467 10,606 39,175 114,248 (a) Represents the amount of the gross carrying value directly written off. For consumer and commercial loans, the loss from a charge-off is measured as the difference between the gross carrying value of a loan and the fair value of the collateral, less costs to sell. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for more information regarding our charge-off policies. (b) Primarily related to the transfer of finance receivables and loans from held-for-investment to held-for-sale. The following table presents information about significant sales of finance receivables and loans and transfers of finance receivables and loans from held-for-investment to held-for-sale. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Consumer automotive $ 28 $ 57 $ 1,326 $ 4,216 Consumer mortgage 3 6 9 12 Commercial — — — 28 Total sales and transfers $ 31 $ 63 $ 1,335 $ 4,256 The following table presents information about significant purchases of finance receivables and loans. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Consumer automotive $ 83 $ — $ 762 $ — Consumer mortgage 1,183 467 2,319 2,855 Total purchases of finance receivables and loans $ 1,266 $ 467 $ 3,081 $ 2,855 The following table presents an analysis of our past due finance receivables and loans recorded at gross carrying value. ($ in millions) 30–59 days past due 60–89 days past due 90 days or more past due Total past due Current Total finance receivables and loans September 30, 2017 Consumer automotive $ 1,742 $ 414 $ 261 $ 2,417 $ 64,660 $ 67,077 Consumer mortgage Mortgage Finance 75 1 5 81 9,679 9,760 Mortgage — Legacy 40 21 58 119 2,136 2,255 Total consumer mortgage 115 22 63 200 11,815 12,015 Total consumer 1,857 436 324 2,617 76,475 79,092 Commercial Commercial and industrial Automotive 16 — 13 29 31,956 31,985 Other — — 8 8 3,766 3,774 Commercial real estate — Automotive 3 — — 3 4,017 4,020 Total commercial 19 — 21 40 39,739 39,779 Total consumer and commercial $ 1,876 $ 436 $ 345 $ 2,657 $ 116,214 $ 118,871 December 31, 2016 Consumer automotive $ 1,850 $ 428 $ 302 $ 2,580 $ 63,213 $ 65,793 Consumer mortgage Mortgage Finance 39 6 4 49 8,245 8,294 Mortgage — Legacy 45 18 57 120 2,636 2,756 Total consumer mortgage 84 24 61 169 10,881 11,050 Total consumer 1,934 452 363 2,749 74,094 76,843 Commercial Commercial and industrial Automotive 3 — 7 10 35,031 35,041 Other — — — — 3,248 3,248 Commercial real estate — Automotive — — — — 3,812 3,812 Total commercial 3 — 7 10 42,091 42,101 Total consumer and commercial $ 1,937 $ 452 $ 370 $ 2,759 $ 116,185 $ 118,944 The following table presents the gross carrying value of our finance receivables and loans on nonaccrual status. ($ in millions) September 30, 2017 December 31, 2016 Consumer automotive $ 573 $ 598 Consumer mortgage Mortgage Finance 7 10 Mortgage — Legacy 81 89 Total consumer mortgage 88 99 Total consumer 661 697 Commercial Commercial and industrial Automotive 78 33 Other 61 84 Commercial real estate — Automotive 7 5 Total commercial 146 122 Total consumer and commercial finance receivables and loans $ 807 $ 819 Management performs a quarterly analysis of the consumer automotive, consumer mortgage, and commercial portfolios using a range of credit quality indicators to assess the adequacy of the allowance for loan losses based on historical and current trends. The following tables present the population of loans by quality indicators for our consumer automotive, consumer mortgage, and commercial portfolios. The following table presents performing and nonperforming credit quality indicators in accordance with our internal accounting policies for our consumer finance receivables and loans recorded at gross carrying value. Nonperforming loans include finance receivables and loans on nonaccrual status when the principal or interest has been delinquent for 90 days or when full collection is not expected. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for additional information. September 30, 2017 December 31, 2016 ($ in millions) Performing Nonperforming Total Performing Nonperforming Total Consumer automotive $ 66,504 $ 573 $ 67,077 $ 65,195 $ 598 $ 65,793 Consumer mortgage Mortgage Finance 9,753 7 9,760 8,284 10 8,294 Mortgage — Legacy 2,174 81 2,255 2,667 89 2,756 Total consumer mortgage 11,927 88 12,015 10,951 99 11,050 Total consumer $ 78,431 $ 661 $ 79,092 $ 76,146 $ 697 $ 76,843 The following table presents pass and criticized credit quality indicators based on regulatory definitions for our commercial finance receivables and loans recorded at gross carrying value. September 30, 2017 December 31, 2016 ($ in millions) Pass Criticized (a) Total Pass Criticized (a) Total Commercial and industrial Automotive $ 30,189 $ 1,796 $ 31,985 $ 33,160 $ 1,881 $ 35,041 Other 2,913 861 3,774 2,597 651 3,248 Commercial real estate — Automotive 3,891 129 4,020 3,653 159 3,812 Total commercial $ 36,993 $ 2,786 $ 39,779 $ 39,410 $ 2,691 $ 42,101 (a) Includes loans classified as special mention, substandard, or doubtful. These classifications are based on regulatory definitions and generally represent loans within our portfolio that have a higher default risk or have already defaulted. Impaired Loans and Troubled Debt Restructurings Impaired Loans Loans are considered impaired when we determine it is probable that we will be unable to collect all amounts due according to the terms of the loan agreement. For more information on our impaired finance receivables and loans, refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K. The following table presents information about our impaired finance receivables and loans. ( $ in millions ) Unpaid principal balance (a) Gross carrying value Impaired with no allowance Impaired with an allowance Allowance for impaired loans September 30, 2017 Consumer automotive $ 411 $ 403 $ 86 $ 317 $ 35 Consumer mortgage Mortgage Finance 8 8 4 4 — Mortgage — Legacy 234 229 56 173 30 Total consumer mortgage 242 237 60 177 30 Total consumer 653 640 146 494 65 Commercial Commercial and industrial Automotive 78 78 51 27 3 Other 70 61 10 51 17 Commercial real estate — Automotive 7 7 3 4 1 Total commercial 155 146 64 82 21 Total consumer and commercial finance receivables and loans $ 808 $ 786 $ 210 $ 576 $ 86 December 31, 2016 Consumer automotive $ 407 $ 370 $ 131 $ 239 $ 28 Consumer mortgage Mortgage Finance 8 8 3 5 — Mortgage — Legacy 243 239 56 183 34 Total consumer mortgage 251 247 59 188 34 Total consumer 658 617 190 427 62 Commercial Commercial and industrial Automotive 33 33 7 26 3 Other 99 84 — 84 19 Commercial real estate — Automotive 5 5 2 3 1 Total commercial 137 122 9 113 23 Total consumer and commercial finance receivables and loans $ 795 $ 739 $ 199 $ 540 $ 85 (a) Adjusted for charge-offs. The following tables present average balance and interest income for our impaired finance receivables and loans. 2017 2016 Three months ended September 30, ($ in millions) Average balance Interest income Average balance Interest income Consumer automotive $ 389 $ 5 $ 347 $ 4 Consumer mortgage Mortgage Finance 8 — 8 — Mortgage — Legacy 231 2 245 2 Total consumer mortgage 239 2 253 2 Total consumer 628 7 600 6 Commercial Commercial and industrial Automotive 77 1 48 1 Other 63 — 63 — Commercial real estate — Automotive 7 — 6 — Total commercial 147 1 117 1 Total consumer and commercial finance receivables and loans $ 775 $ 8 $ 717 $ 7 2017 2016 Nine months ended September 30, ($ in millions) Average balance Interest income Average balance Interest income Consumer automotive $ 368 $ 15 $ 340 $ 12 Consumer mortgage Mortgage Finance 8 — 8 — Mortgage — Legacy 236 7 250 7 Total consumer mortgage 244 7 258 7 Total consumer 612 22 598 19 Commercial Commercial and industrial Automotive 55 2 35 1 Other 73 8 58 1 Commercial real estate — Automotive 6 — 6 — Total commercial 134 10 99 2 Total consumer and commercial finance receivables and loans $ 746 $ 32 $ 697 $ 21 Troubled Debt Restructurings Troubled Debt Restructurings (TDRs) are loan modifications where concessions were granted to borrowers experiencing financial difficulties. For automotive loans, we may offer several types of assistance to aid our customers, including extension of the loan maturity date and rewriting the loan terms. Additionally, for mortgage loans, as part of certain programs, we offer mortgage loan modifications to qualified borrowers. These programs are in place to provide support to our mortgage customers in financial distress, including principal forgiveness, maturity extensions, delinquent interest capitalization, and changes to contractual interest rates. Total TDRs recorded at gross carrying value were $715 million and $663 million at September 30, 2017 , and December 31, 2016 , respectively. Commercial commitments to lend additional funds to borrowers whose terms had been modified in a TDR were $7 million and $2 million at September 30, 2017 , and December 31, 2016 , respectively. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for additional information. The following tables present information related to finance receivables and loans recorded at gross carrying value modified in connection with a TDR during the period. 2017 2016 Three months ended September 30, ($ in millions) Number of loans Pre-modification gross carrying value Post-modification gross carrying value Number of loans Pre-modification gross carrying value Post-modification gross carrying value Consumer automotive 7,165 $ 80 $ 75 4,427 $ 70 $ 58 Consumer mortgage Mortgage Finance 2 — — 2 — — Mortgage — Legacy 37 4 4 35 6 6 Total consumer mortgage 39 4 4 37 6 6 Total consumer 7,204 84 79 4,464 76 64 Commercial Commercial and industrial Automotive 3 13 13 — — — Commercial real estate — Automotive 1 3 3 — — — Total commercial 4 16 16 — — — Total consumer and commercial finance receivables and loans 7,208 $ 100 $ 95 4,464 $ 76 $ 64 2017 2016 Nine months ended September 30, ($ in millions) Number of loans Pre-modification gross carrying value Post-modification gross carrying value Number of loans Pre-modification gross carrying value Post-modification gross carrying value Consumer automotive 19,374 $ 298 $ 262 14,816 $ 238 $ 202 Consumer mortgage Mortgage Finance 3 — — 5 2 2 Mortgage — Legacy 109 19 18 92 14 14 Total consumer mortgage 112 19 18 97 16 16 Total consumer 19,486 317 280 14,913 254 218 Commercial Commercial and industrial Automotive 3 13 13 — — — Other 2 44 44 — — — Commercial real estate — Automotive 1 3 3 — — — Total commercial 6 60 60 — — — Total consumer and commercial finance receivables and loans 19,492 $ 377 $ 340 14,913 $ 254 $ 218 The following tables present information about finance receivables and loans recorded at gross carrying value that have redefaulted during the reporting period and were within 12 months or less of being modified as a TDR. Redefault is when finance receivables and loans meet the requirements for evaluation under our charge-off policy (refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for additional information) except for commercial finance receivables and loans, where redefault is defined as 90 days past due. 2017 2016 Three months ended September 30, ($ in millions) Number of loans Gross carrying value Charge-off amount Number of loans Gross carrying value Charge-off amount Consumer automotive 2,222 $ 25 $ 18 1,959 $ 23 $ 14 Consumer mortgage Mortgage Finance — — — — — — Mortgage — Legacy 1 — — 1 — — Total consumer finance receivables and loans 2,223 $ 25 $ 18 1,960 $ 23 $ 14 2017 2016 Nine months ended September 30, ($ in millions) Number of loans Gross carrying value Charge-off amount Number of loans Gross carrying value Charge-off amount Consumer automotive 6,354 $ 74 $ 51 5,617 $ 69 $ 39 Consumer mortgage Mortgage Finance 1 1 — — — — Mortgage — Legacy 1 — — 4 — — Total consumer finance receivables and loans 6,356 $ 75 $ 51 5,621 $ 69 $ 39

Investment in Operating Leases,

Investment in Operating Leases, Net	9 Months Ended
	Sep. 30, 2017
Leases, Operating [Abstract]
Lessor, Operating Leases [Text Block]	Investment in Operating Leases, Net Investments in operating leases were as follows. ($ in millions) September 30, 2017 December 31, 2016 Vehicles $ 11,001 $ 14,584 Accumulated depreciation (2,070 ) (3,114 ) Investment in operating leases, net $ 8,931 $ 11,470 Depreciation expense on operating lease assets includes remarketing gains and losses recognized on the sale of operating lease assets. The following summarizes the components of depreciation expense on operating lease assets. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Depreciation expense on operating lease assets (excluding remarketing gains) $ 323 $ 470 $ 1,062 $ 1,555 Remarketing gains (51 ) (62 ) (80 ) (203 ) Net depreciation expense on operating lease assets $ 272 $ 408 $ 982 $ 1,352

Securitizations and Variable In

Securitizations and Variable Interest Entities	9 Months Ended
	Sep. 30, 2017
Securitizations And Variable Interest Entities [Abstract]
Variable Interest Entity Disclosure [Text Block]	Securitizations and Variable Interest Entities We are involved in several types of securitization and financing transactions that utilize special-purpose entities (SPEs). A SPE is a legal entity that is designed to fulfill a specified limited need of the sponsor. Our principal use of SPEs is to obtain liquidity by securitizing certain of our financial assets and operating lease assets. The transaction-specific SPEs involved in our securitization and other financing transactions are often considered VIEs. VIEs are entities that have either a total equity investment at risk that is insufficient to permit the entity to finance its activities without additional subordinated financial support or whose equity investors at risk lack the ability to control the entity's activities. We securitize consumer and commercial automotive loans, and operating leases through private-label securitizations. We often securitize these loans and notes secured by operating leases (collectively referred to as financial assets) through the use of securitization entities, which may or may not be consolidated on our Condensed Consolidated Balance Sheet. The pretax gain on sales of financial assets into nonconsolidated consumer automotive securitization trusts was $0 million and $2 million for the three months and nine months ended September 30, 2017 , respectively. There were no pretax gains or losses for the three months and nine months ended September 30, 2016 . We provide long-term guarantee contracts to investors in certain nonconsolidated affordable housing entities and have extended a line of credit to provide liquidity. Since we do not have control over the entities or the power to make decisions, we do not consolidate the entities and our involvement is limited to the guarantee and the line of credit. We have involvement with various other nonconsolidated equity investments, including affordable housing entities and venture capital funds and loan funds. We do not consolidate these entities and our involvement is limited to our outstanding investment, additional capital committed to these funds plus any previously recognized low income housing tax credits that are subject to recapture. Refer to Note 11 to the Consolidated Financial Statements included in our 2016 Annual Report on Form 10-K for further description of our securitization activities and our involvement with VIEs. The following table presents our involvement in consolidated and nonconsolidated VIEs in which we hold variable interests. For additional detail related to the assets and liabilities of consolidated variable interest entities refer to the Condensed Consolidated Balance Sheet. ($ in millions) Carrying value of total assets Carrying value of total liabilities Assets sold to nonconsolidated VIEs (a) Maximum exposure to loss in nonconsolidated VIEs September 30, 2017 On-balance sheet variable interest entities Consumer automotive $ 17,462 (b) $ 7,529 (c) Commercial automotive 12,590 2,557 Off-balance sheet variable interest entities Consumer automotive 42 (d) — $ 2,293 $ 2,334 (e) Commercial other 575 (f) 238 (g) — 756 (h) Total $ 30,669 $ 10,324 $ 2,293 $ 3,090 December 31, 2016 On-balance sheet variable interest entities Consumer automotive $ 20,869 (b) $ 8,557 (c) Commercial automotive 16,278 4,764 Off-balance sheet variable interest entities Consumer automotive 24 (f) — $ 2,899 $ 2,923 (e) Commercial other 460 (f) 169 (g) — 651 (h) Total $ 37,631 $ 13,490 $ 2,899 $ 3,574 (a) Asset values represent the current unpaid principal balance of outstanding consumer finance receivables and loans within the VIEs. (b) Includes $8.4 billion and $9.6 billion of assets that are not encumbered by VIE beneficial interests held by third parties at September 30, 2017 , and December 31, 2016 , respectively. Ally or consolidated affiliates hold the interests in these assets. (c) Includes $30 million and $50 million of liabilities that are not obligations to third-party beneficial interest holders at September 30, 2017 , and December 31, 2016 , respectively. (d) Represents retained notes and certificated residual interests, of which $40 million is classified as held-to-maturity securities and $2 million is classified as other assets at September 30, 2017 . These assets represent our compliance with the risk retention rules under the Dodd-Frank Act, requiring us to retain at least five percent of the credit risk of the assets underlying asset-backed securitizations , which became effective on December 24, 2016. (e) Maximum exposure to loss represents the current unpaid principal balance of outstanding loans, retained notes, certificated residual interests, as well as certain noncertificated interests retained from the sale of automotive finance receivables. This measure is based on the very unlikely event that all of our sold loans have defects that would trigger a representation and warranty provision and the underlying collateral supporting the loans becomes worthless. This required disclosure is not an indication of our expected loss. (f) Amounts are classified as other assets. (g) Amounts are classified as accrued expenses and other liabilities. (h) For certain nonconsolidated affordable housing entities, maximum exposure to loss represents the yield we guaranteed investors through long-term guarantee contracts. The amount disclosed is based on the unlikely event that the underlying properties cease generating yield to investors and the yield delivered to investors in the form of low income tax housing credits is recaptured. For nonconsolidated equity investments, maximum exposure to loss represents our outstanding investment, additional committed capital, and low income housing tax credits subject to recapture. The amount disclosed is based on the unlikely event that our committed capital is funded, our investments become worthless, and the tax credits previously delivered to us are recaptured. This required disclosure is not an indication of our expected loss. Cash Flows with Off-balance Sheet Securitization Entities The following table summarizes cash flows received and paid related to securitization entities and asset-backed financings where the transfer is accounted for as a sale and we have a continuing involvement with the transferred assets (e.g., servicing) that were outstanding during the nine months ended September 30, 2017 , and 2016 . Additionally, this table contains information regarding cash flows received from and paid to nonconsolidated securitization entities that existed during each period. Nine months ended September 30, ($ in millions) Consumer automotive 2017 Cash proceeds from transfers completed during the period $ 1,187 Cash disbursements for repurchases during the period (a) (491 ) Servicing fees 25 Cash flows received on retained interests in securitization entities 16 Other cash flows 4 2016 Cash proceeds from transfers completed during the period $ 1,659 Servicing fees 27 Other cash flows 6 (a) During the second quarter of 2017, we elected to not renew a retail automotive credit conduit facility and also purchased the related retail automotive loans and settled associated retained interests. Delinquencies and Net Credit Losses The following tables represent on-balance sheet finance receivables and loans, off-balance sheet securitizations, and whole-loan sales where we have continuing involvement. The tables present quantitative information about delinquencies and net credit losses. Total amount Amount 60 days or more past due ($ in millions) September 30, 2017 December 31, 2016 September 30, 2017 December 31, 2016 On-balance sheet finance receivables and loans Consumer automotive $ 67,077 $ 65,793 $ 675 $ 730 Consumer mortgage 12,015 11,050 85 85 Commercial automotive 36,005 38,853 13 7 Commercial other 3,774 3,248 8 — Total on-balance sheet finance receivables and loans 118,871 118,944 781 822 Off-balance sheet securitization entities Consumer automotive 2,293 2,392 14 13 Total off-balance sheet securitization entities 2,293 2,392 14 13 Whole-loan sales (a) 1,655 3,164 4 6 Total $ 122,819 $ 124,500 $ 799 $ 841 (a) Whole-loan sales are not part of a securitization transaction, but represent consumer automotive pools of loans sold to third-party investors. Net credit losses Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 On-balance sheet finance receivables and loans Consumer automotive $ 242 $ 219 $ 692 $ 540 Consumer mortgage 1 (6 ) 3 4 Commercial automotive 1 — 1 — Commercial other 9 — 9 — Total on-balance sheet finance receivables and loans 253 213 705 544 Off-balance sheet securitization entities Consumer automotive 3 2 9 6 Total off-balance sheet securitization entities 3 2 9 6 Whole-loan sales (a) 1 1 3 2 Total $ 257 $ 216 $ 717 $ 552 (a) Whole-loan sales are not part of a securitization transaction, but represent consumer automotive pools of loans sold to third-party investors.

Servicing Activities

Servicing Activities	9 Months Ended
	Sep. 30, 2017
Servicing Asset [Abstract]
Servicing Activities [Text Block]	Servicing Activities Automotive Finance Servicing Activities We service consumer automotive contracts. Historically, we have sold a portion of our consumer automotive contracts. With respect to contracts we sell, we generally retain the right to service and earn a servicing fee for our servicing function. We have concluded that the fee we are paid for servicing consumer automotive finance receivables represents adequate compensation, and consequently, we do not recognize a servicing asset or liability. We recognized automotive servicing fee income of $11 million and $41 million during the three months and nine months ended September 30, 2017 , respectively, compared to $18 million and $49 million during the three months and nine months ended September 30, 2016 . Automotive Finance Serviced Assets The current unpaid principal balance and any related unamortized deferred fees and costs of total serviced automotive finance loans and leases outstanding were as follows. ($ in millions) September 30, 2017 December 31, 2016 On-balance sheet automotive finance loans and leases Consumer automotive $ 66,721 $ 65,646 Commercial automotive 36,005 38,853 Operating leases 8,853 11,311 Other 71 67 Off-balance sheet automotive finance loans Securitizations 2,312 2,412 Whole-loan sales 1,668 3,191 Total serviced automotive finance loans and leases $ 115,630 $ 121,480

Other Assets

Other Assets	9 Months Ended
	Sep. 30, 2017
Other Assets [Abstract]
Other Assets Disclosure [Text Block]	Other Assets The components of other assets were as follows. ($ in millions) September 30, 2017 December 31, 2016 Property and equipment at cost $ 1,024 $ 901 Accumulated depreciation (587 ) (525 ) Net property and equipment 437 376 Restricted cash collections for securitization trusts (a) 1,260 1,694 Nonmarketable equity investments (b) 1,065 1,046 Net deferred tax assets 659 994 Accrued interest and rent receivables 508 476 Goodwill (c) 240 240 Other accounts receivable 212 100 Cash reserve deposits held for securitization trusts (d) 120 184 Restricted cash and cash equivalents 112 111 Fair value of derivative contracts in receivable position (e) 37 95 Cash collateral placed with counterparties 20 167 Other assets 1,393 1,371 Total other assets $ 6,063 $ 6,854 (a) Represents cash collections from customer payments on securitized receivables. These funds are distributed to investors as payments on the related secured debt. (b) Includes investments in FHLB stock of $581 million and $577 million at September 30, 2017 , and December 31, 2016 , respectively; and Federal Reserve Bank (FRB) stock of $445 million and $435 million at September 30, 2017 , and December 31, 2016 , respectively. (c) Includes goodwill of $27 million within our Insurance operations at both September 30, 2017 , and December 31, 2016 ; $193 million within Corporate and Other at both September 30, 2017 , and December 31, 2016 ; and $20 million within Automotive Finance operations at both September 30, 2017 , and December 31, 2016 . No changes to the carrying amount of goodwill were recorded during the nine months ended September 30, 2017 . (d) Represents credit enhancement in the form of cash reserves for various securitization transactions. (e) For additional information on derivative instruments and hedging activities, refer to Note 19 .

Deposit Liabilities

Deposit Liabilities	9 Months Ended
	Sep. 30, 2017
Deposits [Abstract]
Deposit Liabilities Disclosures [Text Block]	Deposit Liabilities Deposit liabilities consisted of the following. ( $ in millions ) September 30, 2017 December 31, 2016 Noninterest-bearing deposits $ 129 $ 84 Interest-bearing deposits Savings and money market checking accounts 50,287 46,976 Certificates of deposit 39,686 31,795 Dealer deposits 14 167 Total deposit liabilities $ 90,116 $ 79,022 At September 30, 2017 , and December 31, 2016 , certificates of deposit included $16.2 billion and $12.1 billion , respectively, of those in denominations of $100 thousand or more. At September 30, 2017 , and December 31, 2016 , certificates of deposit included $4.5 billion and $3.5 billion , respectively, of those in denominations in excess of $250 thousand federal insurance limits.

Debt

Debt	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	Debt Short-term Borrowings The following table presents the composition of our short-term borrowings portfolio. September 30, 2017 December 31, 2016 ($ in millions) Unsecured Secured (a) Total Unsecured Secured (a) Total Demand notes $ 3,379 $ — $ 3,379 $ 3,622 $ — $ 3,622 Federal Home Loan Bank — 5,625 5,625 — 7,875 7,875 Financial instruments sold under agreements to repurchase — 1,171 1,171 — 1,176 1,176 Total short-term borrowings $ 3,379 $ 6,796 $ 10,175 $ 3,622 $ 9,051 $ 12,673 (a) Refer to the section below titled Long-term Debt for further details on assets restricted as collateral for payment of the related debt. We periodically enter into term repurchase agreements, short-term borrowing agreements in which we sell financial instruments to one or more investors while simultaneously committing to repurchase them at a specified future date, at the stated price plus accrued interest. As of September 30, 2017 , the financial instruments sold under agreements to repurchase consisted of $537 million of U.S. Treasury securities set to mature within the next 30 days, and $634 million of agency mortgage-backed residential debt securities set to mature as follows: $480 million within the next 30 days , and $154 million within 31 to 60 day s. Refer to Note 7 and Note 22 for further details. Additionally, in December 2016, we sold asset-backed automotive financial instruments, which are our retained interests from certain on-balance sheet securitizations, subject to a repurchase agreement in exchange for $500 million , which was recorded as a short-term secured borrowing. The asset-backed automotive financial instruments that we sold subject to the repurchase agreement were secured by finance receivables that we have securitized. Refer to Note 10 for additional information on our securitization activities. This repurchase agreement was terminated in September 2017. The primary risk associated with these repurchase agreements is that the counterparty will be unable to perform under the terms of the contract. As the borrower, we are exposed to the excess market value of the securities pledged over the amount borrowed. Daily mark-to-market collateral management is designed to limit this risk to the initial margin. However, should a counterparty declare bankruptcy or become insolvent, we may incur additional delays and costs. As of September 30, 2017 , we placed cash collateral totaling $10 million with counterparties under these collateral arrangements associated with our repurchase agreements. Long-term Debt The following table presents the composition of our long-term debt portfolio. September 30, 2017 December 31, 2016 ($ in millions) Unsecured Secured Total Unsecured Secured Total Long-term debt Due within one year $ 3,828 $ 6,642 $ 10,470 $ 4,274 $ 10,279 $ 14,553 Due after one year (a) 13,129 21,249 34,378 15,450 23,810 39,260 Fair value adjustment (b) 289 (15 ) 274 326 (11 ) 315 Total long-term debt (c) $ 17,246 $ 27,876 $ 45,122 $ 20,050 $ 34,078 $ 54,128 (a) Includes $2.6 billion of trust preferred securities at both September 30, 2017 , and December 31, 2016 . (b) Represents the fair value adjustment associated with the application of hedge accounting on certain of our long-term debt positions. Refer to Note 19 for additional information. (c) Includes advances from the FHLB of Pittsburgh of $8.4 billion and $6.1 billion at September 30, 2017 , and December 31, 2016 , respectively. The following table presents the scheduled remaining maturity of long-term debt at September 30, 2017 , assuming no early redemptions will occur. The actual payment of secured debt may vary based on the payment activity of the related pledged assets. ($ in millions) 2017 2018 2019 2020 2021 2022 and thereafter Fair value adjustment Total Unsecured Long-term debt $ 1,590 $ 3,582 $ 1,680 $ 2,252 $ 637 $ 8,475 $ 289 $ 18,505 Original issue discount (24 ) (100 ) (39 ) (39 ) (43 ) (1,014 ) — (1,259 ) Total unsecured 1,566 3,482 1,641 2,213 594 7,461 289 17,246 Secured Long-term debt 1,048 7,379 7,617 6,818 3,179 1,850 (15 ) 27,876 Total long-term debt $ 2,614 $ 10,861 $ 9,258 $ 9,031 $ 3,773 $ 9,311 $ 274 $ 45,122 The following summarizes assets restricted as collateral for the payment of the related debt obligation primarily arising from securitization transactions accounted for as secured borrowings and repurchase agreements. September 30, 2017 December 31, 2016 ($ in millions) Total (a) Ally Bank Total (a) Ally Bank Investment securities (b) $ 6,676 $ 5,482 $ 4,895 $ 4,231 Mortgage assets held-for-investment and lending receivables 11,888 11,888 10,954 10,954 Consumer automotive finance receivables (b) 21,261 4,818 27,846 5,751 Commercial automotive finance receivables 16,142 16,018 19,487 19,280 Investment in operating leases, net 737 7 2,040 913 Total assets restricted as collateral (c) (d) $ 56,704 $ 38,213 $ 65,222 $ 41,129 Secured debt $ 34,672 (e) $ 18,781 $ 43,129 (e) $ 22,149 (a) Ally Bank is a component of the total column. (b) A portion of the restricted investment securities at September 30, 2017 , and December 31, 2016 , and consumer automotive finance receivables at December 31, 2016 , were restricted under repurchase agreements. Refer to the section above titled Short-term Borrowings for information on the repurchase agreements. (c) Ally Bank has an advance agreement with the FHLB, and had assets pledged to secure borrowings that were restricted as collateral to the FHLB totaling $21.4 billion and $19.0 billion at September 30, 2017 , and December 31, 2016 , respectively. These assets were composed primarily of consumer mortgage finance receivables and loans and investment securities. Ally Bank has access to the FRB Discount Window. Ally Bank had assets pledged and restricted as collateral to the FRB totaling $2.3 billion and $2.4 billion at September 30, 2017 , and December 31, 2016 , respectively. These assets were composed of consumer automotive finance receivables and loans and operating lease assets. Availability under these programs is only for the operations of Ally Bank and cannot be used to fund the operations or liabilities of Ally or its subsidiaries. (d) Excludes restricted cash and cash reserves for securitization trusts recorded within other assets on the Condensed Consolidated Balance Sheet . Refer to Note 12 for additional information. (e) Includes $6.8 billion and $9.1 billion of short-term borrowings at September 30, 2017 , and December 31, 2016 , respectively. Trust Preferred Securities At September 30, 2017 , we have issued and outstanding approximately $2.6 billion in aggregate liquidation preference of 8.125% Fixed Rate / Floating Rate Trust Preferred Securities, Series 2 (Series 2 TRUPS). Each Series 2 TRUPS security has a liquidation amount of $25. Distributions are cumulative and are payable until redemption at the applicable coupon rate. Distributions were payable at an annual rate of 8.125% payable quarterly in arrears, through but excluding February 15, 2016. From and including February 15, 2016, to but excluding February 15, 2040, distributions will be payable at an annual rate equal to three-month London interbank offer rate plus 5.785% payable quarterly in arrears, beginning May 15, 2016. Ally has the right to defer payments of interest for a period not exceeding 20 consecutive quarters. The Series 2 TRUPS have no stated maturity date, but must be redeemed upon the redemption or maturity of the related debentures (Debentures), which mature on February 15, 2040. Ally at any time on or after February 15, 2016, may redeem the Series 2 TRUPS at a redemption price equal to 100% of the principal amount being redeemed, plus accrued and unpaid interest through the date of redemption. The Series 2 TRUPS are generally nonvoting, other than with respect to certain limited matters. During any period in which any Series 2 TRUPS remain outstanding but in which distributions on the Series 2 TRUPS have not been fully paid, none of Ally or its subsidiaries will be permitted to (i) declare or pay dividends on, make any distributions with respect to, or redeem, purchase, acquire or otherwise make a liquidation payment with respect to, any of Ally’s capital stock or make any guarantee payment with respect thereto; or (ii) make any payments of principal, interest, or premium on, or repay, repurchase or redeem, any debt securities or guarantees that rank on a parity with or junior in interest to the Debentures with certain specified exceptions in each case. Funding Facilities We utilize both committed credit facilities and other collateralized funding vehicles. The debt outstanding under our various funding facilities is included on our Condensed Consolidated Balance Sheet . As of September 30, 2017 , Ally Bank had exclusive access to $3.7 billion of funding capacity from committed credit facilities. Funding programs supported by the FRB and the FHLB complement Ally Bank’s private collateralized funding vehicles. The total capacity in our committed funding facilities is provided by banks through private transactions. The committed secured funding facilities can be revolving in nature and allow for additional funding during the commitment period, or they can be amortizing and not allow for any further funding after the closing date. At September 30, 2017 , all of our $14.7 billion of committed capacity was revolving. Our revolving facilities generally have an original tenor ranging from 364 days to two years. As of September 30, 2017 , we had $2.6 billion of committed funding capacity from revolving facilities with a remaining tenor greater than 364 days. Committed Funding Facilities Outstanding Unused capacity (a) Total capacity ($ in millions) September 30, 2017 December 31, 2016 September 30, 2017 December 31, 2016 September 30, 2017 December 31, 2016 Bank funding Secured (b) $ 1,350 $ 3,250 $ 2,325 $ 350 $ 3,675 $ 3,600 Parent funding Secured 8,180 11,550 2,820 1,975 11,000 13,525 Unsecured — — — 1,250 — 1,250 Total committed facilities $ 9,530 $ 14,800 $ 5,145 $ 3,575 $ 14,675 $ 18,375 (a) Funding from committed secured facilities is available on request in the event excess collateral resides in certain facilities or the extent incremental collateral is available and contributed to the facilities. (b) Excludes off-balance sheet credit facility amounts.

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	9 Months Ended
	Sep. 30, 2017
Accounts Payable and Accrued Liabilities [Abstract]
Accounts Payable and Accrued Liabilities Disclosure [Text Block]	Accrued Expenses and Other Liabilities The components of accrued expenses and other liabilities were as follows. ( $ in millions ) September 30, 2017 December 31, 2016 Accounts payable $ 863 $ 649 Employee compensation and benefits 227 232 Reserves for insurance losses and loss adjustment expenses 173 149 Deferred revenue 34 56 Fair value of derivative contracts in payable position (a) 30 95 Cash collateral received from counterparties 14 10 Other liabilities 551 546 Total accrued expenses and other liabilities $ 1,892 $ 1,737 (a) For additional information on derivative instruments and hedging activities, refer to Note 19 .

Accumulated Other Comprehensive

Accumulated Other Comprehensive (Loss) Income	9 Months Ended
	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Abstract]
Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive (Loss) Income The following table presents changes, net of tax, in each component of accumulated other comprehensive (loss) income. ($ in millions) Unrealized (losses) gains on investment securities (a) Translation adjustments and net investment hedges (b) Cash flow hedges (b) Defined benefit pension plans Accumulated other comprehensive (loss) income Balance at December 31, 2015 $ (159 ) $ 9 $ 8 $ (89 ) $ (231 ) 2016 net change 258 5 — (1 ) 262 Balance at September 30, 2016 $ 99 $ 14 $ 8 $ (90 ) $ 31 Balance at December 31, 2016 $ (273 ) $ 14 $ 8 $ (90 ) $ (341 ) 2017 net change 142 2 1 (1 ) 144 Balance at September 30, 2017 $ (131 ) $ 16 $ 9 $ (91 ) $ (197 ) (a) Represents the after-tax difference between the fair value and amortized cost of our available-for-sale securities portfolio. (b) For additional information on derivative instruments and hedging activities, refer to Note 19 . The following tables present the before- and after-tax changes in each component of accumulated other comprehensive (loss) income. Three months ended September 30, 2017 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 95 $ (22 ) $ 73 Less: Net realized gains reclassified to income from continuing operations 25 (a) 2 (b) 27 Net change 70 (24 ) 46 Translation adjustments Net unrealized gains arising during the period 8 (3 ) 5 Net investment hedges (c) Net unrealized losses arising during the period (6 ) 3 (3 ) Cash flow hedges (c) Net unrealized gains arising during the period 1 (1 ) — Other comprehensive income $ 73 $ (25 ) $ 48 (a) Includes gains reclassified to other gain on investments, net in our Condensed Consolidated Statement of Comprehensive Income . (b) Includes amounts reclassified to income tax expense from continuing operations in our Condensed Consolidated Statement of Comprehensive Income . (c) For additional information on derivative instruments and hedging activities, refer to Note 19 . Three months ended September 30, 2016 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 41 $ (4 ) $ 37 Less: Net realized gains reclassified to income from continuing operations 52 (a) (11 ) (b) 41 Net change (11 ) 7 (4 ) Translation adjustments Net unrealized losses arising during the period (2 ) 1 (1 ) Net investment hedges (c) Net unrealized gains arising during the period 2 (1 ) 1 Other comprehensive income $ (11 ) $ 7 $ (4 ) (a) Includes gains reclassified to other gain on investments, net in our Condensed Consolidated Statement of Comprehensive Income . (b) Includes amounts reclassified to income tax expense from continuing operations in our Condensed Consolidated Statement of Comprehensive Income . (c) For additional information on derivative instruments and hedging activities, refer to Note 19 . Nine months ended September 30, 2017 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 278 $ (64 ) $ 214 Less: Net realized gains reclassified to income from continuing operations 75 (a) (3 ) (b) 72 Net change 203 (61 ) 142 Translation adjustments Net unrealized gains arising during the period 14 (5 ) 9 Net investment hedges (c) Net unrealized losses arising during the period (12 ) 5 (7 ) Cash flow hedges (c) Net unrealized gains arising during the period 2 (1 ) 1 Defined benefit pension plans Net unrealized losses arising during the period (1 ) — (1 ) Other comprehensive income $ 206 $ (62 ) $ 144 (a) Includes gains reclassified to other gain on investments, net in our Condensed Consolidated Statement of Comprehensive Income . (b) Includes amounts reclassified to income tax expense from continuing operations in our Condensed Consolidated Statement of Comprehensive Income . (c) For additional information on derivative instruments and hedging activities, refer to Note 19 . Nine months ended September 30, 2016 ($ in millions) Before Tax Tax Effect After Tax Investment securities Net unrealized gains arising during the period $ 506 $ (133 ) $ 373 Less: Net realized gains reclassified to income from continuing operations 145 (a) (30 ) (b) 115 Net change 361 (103 ) 258 Translation adjustments Net unrealized gains arising during the period 10 (4 ) 6 Less: Net realized losses reclassified to income from discontinued operations, net of tax (1 ) — (1 ) Net change 11 (4 ) 7 Net investment hedges (c) Net unrealized losses arising during the period (4 ) 2 (2 ) Defined benefit pension plans Net unrealized losses arising during the period (1 ) — (1 ) Other comprehensive income $ 367 $ (105 ) $ 262 (a) Includes gains reclassified to other gain on investments, net in our Condensed Consolidated Statement of Comprehensive Income . (b) Includes amounts reclassified to income tax expense from continuing operations in our Condensed Consolidated Statement of Comprehensive Income . (c) For additional information on derivative instruments and hedging activities, refer to Note 19 .

Earnings per Common Share

Earnings per Common Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	Earnings per Common Share The following table presents the calculation of basic and diluted earnings per common share. Three months ended September 30, Nine months ended September 30, ($ in millions, except per share data; shares in thousands) (a) 2017 2016 2017 2016 Net income from continuing operations $ 280 $ 261 $ 747 $ 865 Preferred stock dividends — — — (30 ) Net income from continuing operations attributable to common shareholders 280 261 747 835 Income (loss) from discontinued operations, net of tax 2 (52 ) 1 (46 ) Net income attributable to common shareholders $ 282 $ 209 $ 748 $ 789 Basic weighted-average common shares outstanding (b) 449,169 482,393 457,612 483,993 Diluted weighted-average common shares outstanding (b) 451,078 483,575 458,848 484,762 Basic earnings per common share Net income from continuing operations $ 0.62 $ 0.54 $ 1.63 $ 1.73 Income (loss) from discontinued operations, net of tax — (0.11 ) — (0.10 ) Net income $ 0.63 $ 0.43 $ 1.63 $ 1.63 Diluted earnings per common share Net income from continuing operations $ 0.62 $ 0.54 $ 1.63 $ 1.72 Income (loss) from discontinued operations, net of tax — (0.11 ) — (0.10 ) Net income $ 0.63 $ 0.43 $ 1.63 $ 1.63 (a) Figures in the table may not recalculate exactly due to rounding. Earnings per share is calculated based on unrounded numbers. (b) Includes shares related to share-based compensation that vested but were not yet issued for the three months and nine months ended September 30, 2017 , and 2016 .

Regulatory Capital and Other Re

Regulatory Capital and Other Regulatory Matters	9 Months Ended
	Sep. 30, 2017
Regulatory Capital Requirements [Abstract]
Regulatory Capital Requirements under Banking Regulations [Text Block]	Regulatory Capital and Other Regulatory Matters As a BHC, we and our wholly-owned state-chartered banking subsidiary, Ally Bank, are subject to capital requirements issued by U.S. banking regulators that require us to maintain risk-based and leverage capital ratios above minimum levels. A risk-based capital ratio is a ratio of a banking organization’s regulatory capital to its risk-weighted assets. A leverage capital ratio is a ratio of a banking organization’s regulatory capital to a measure of assets or exposures that is not risk-weighted. As of January 1, 2015, Ally and Ally Bank became subject to the rules implementing the 2010 Basel III capital framework in the United States (U.S. Basel III), which generally reflects higher capital requirements, capital buffers, and changes to regulatory capital definitions, deductions and adjustments, relative to the predecessor requirements implementing the Basel I capital framework in the United States. Certain aspects of U.S. Basel III, including the capital buffers and certain regulatory capital deductions, are subject to a phase-in period through December 31, 2018. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary action by regulators that, if undertaken, could have a direct material effect on the Condensed Consolidated Financial Statements or the results of operations and financial condition of Ally and Ally Bank. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, we and Ally Bank must meet specific capital guidelines that involve quantitative measures of capital, assets and certain off-balance sheet items. These measures and related classifications, which are used in the calculation of our risk-based and leverage capital ratios and those of Ally Bank, are also subject to qualitative judgments by the regulators about the components of capital, the risk-weightings of assets and other exposures, and other factors. The FRB also uses these ratios and guidelines as part of the capital planning and stress testing processes. In addition, in order for Ally to maintain its status as a FHC, Ally and its bank subsidiary, Ally Bank, must remain “well-capitalized” and “well-managed,” as defined under applicable laws. The “well-capitalized” standard for insured depository institutions, such as Ally Bank, reflects the capital requirements under U.S. Basel III. Under U.S. Basel III, Ally must maintain a minimum Common Equity Tier 1 risk-based capital ratio of 4.5% , a minimum Tier 1 risk-based capital ratio of 6% , and a minimum Total risk-based capital ratio of 8% . In addition to these minimum requirements, Ally is also subject to a Common Equity Tier 1 capital conservation buffer of more than 2.5% , subject to a phase-in period from January 1, 2016, through December 31, 2018. Failure to maintain the full amount of the buffer will result in restrictions on Ally’s ability to make capital distributions, including dividend payment and stock repurchases and redemptions, and to pay discretionary bonuses to executive officers. In addition to these new risk-based capital standards, U.S. Basel III subjects all U.S. banking organizations, including Ally, to a minimum Tier 1 leverage ratio of 4% , the denominator of which takes into account only on-balance sheet assets. U.S. Basel III also revised the eligibility criteria for regulatory capital instruments and provides for the phase-out of instruments that had previously been recognized as capital but that do not satisfy these criteria. Subject to certain exceptions (e.g., for certain debt or equity issued to the U.S. government under the Emergency Economic Stabilization Act), trust preferred and other “hybrid” securities are no longer included in a BHC's Tier 1 capital as of January 1, 2016. Also, subject to a phase-in schedule, certain items are deducted from Common Equity Tier 1 capital that had not previously been deducted from regulatory capital, and certain other deductions from regulatory capital have been modified. Among other things, U.S. Basel III requires significant investments in the common shares of unconsolidated financial institutions, mortgage servicing assets, and certain deferred tax assets that exceed specified individual and aggregate thresholds to be deducted from Common Equity Tier 1 capital. U.S. Basel III also revised the standardized approach for calculating risk-weighted assets by, among other things, modifying certain risk weights and the methods for calculating risk-weighted assets for certain types of assets and exposures. Ally is subject to the U.S. Basel III standardized approach for credit risk, but is not subject to the U.S. Basel III advanced approaches for credit risk. Ally is currently not subject to the U.S. market risk capital rule, which applies only to banking organizations with significant trading assets and liabilities. On September 27, 2017, the FRB released a proposal to simplify certain capital requirements, including the requirements related to the above-mentioned capital deductions and adjustments for investments in unconsolidated financial institutions, mortgage servicing assets, and certain deferred tax assets. In addition, on August 22, 2017, the FRB proposed an amendment to the transition provisions of the U.S. Basel III capital rules that would, in anticipation of the simplification proposal, indefinitely postpone certain phase-in requirements for provisions related to the simplification proposal, including the provisions related to the above-mentioned capital deductions and adjustments. Both the simplification proposal and the proposed transitions amendments would primarily apply to non-advanced approaches banking organizations such as Ally. We are evaluating the effect these proposals would have on our regulatory capital position. On March 7, 2016, Ally Bank received approval from the FRB to become a state member bank. Ally Bank is now regulated by the FRB through the Federal Reserve Bank of Chicago, as well as the Utah Department of Financial Institutions (UDFI). As a requirement of FRB membership, we held $445 million of FRB stock at September 30, 2017. In addition, in connection with the application for membership in the Federal Reserve System, Ally Bank made commitments to the FRB relating to capital, liquidity, and business plan requirements. These commitments were consistent with the prior requirements under the now-terminated Capital and Liquidity Maintenance Agreement with the Federal Deposit Insurance Corporation (FDIC), including the requirement to maintain capital at a level such that Ally Bank’s Tier 1 leverage ratio was at least 15% . On August 22, 2017, the FRB lifted the capital, liquidity, and business plan commitments that Ally Bank made in connection with its application for membership in the Federal Reserve System, including the commitment to maintain a Tier 1 leverage ratio of at least 15% . As a result of this development, during the three months ended September 30, 2017, Ally Bank paid a dividend of $2.9 billion to Ally Financial Inc., which was utilized to reduce less cost-efficient borrowings and further enhance our funding profile. Compliance with capital requirements is a strategic priority for Ally. We expect to be in compliance with all applicable requirements within the established timeframes. The following table summarizes our capital ratios under the U.S. Basel III capital framework. September 30, 2017 December 31, 2016 Required minimum Well-capitalized minimum ( $ in millions ) Amount Ratio Amount Ratio Capital ratios Common Equity Tier 1 (to risk-weighted assets) Ally Financial Inc. $ 13,175 9.72 % $ 12,978 9.37 % 4.50 % (a) Ally Bank 16,454 15.39 17,888 16.70 4.50 6.50 % Tier 1 (to risk-weighted assets) Ally Financial Inc. $ 15,539 11.46 % $ 15,147 10.93 % 6.00 % 6.00 % Ally Bank 16,454 15.39 17,888 16.70 6.00 8.00 Total (to risk-weighted assets) Ally Financial Inc. $ 17,891 13.19 % $ 17,419 12.57 % 8.00 % 10.00 % Ally Bank 17,215 16.10 18,458 17.24 8.00 10.00 Tier 1 leverage (to adjusted quarterly average assets) (b) Ally Financial Inc. $ 15,539 9.51 % $ 15,147 9.54 % 4.00 % (a) Ally Bank 16,454 12.89 17,888 15.21 4.00 (c) 5.00 % (a) Currently, there is no ratio component for determining whether a BHC is "well-capitalized." (b) Federal regulatory reporting guidelines require the calculation of adjusted quarterly average assets using a daily average methodology. (c) On August 22, 2017, the FRB lifted the capital, liquidity, and business plan commitments that Ally Bank made in connection with its application for membership in the Federal Reserve System, including the commitment to maintain a Tier 1 leverage ratio of at least 15% . Ally Bank now manages its capital and liquidity subject to applicable regulatory requirements. At September 30, 2017 , Ally and Ally Bank were “well-capitalized” and met all applicable capital requirements to which each was subject. Capital Planning and Stress Tests As a BHC with $50 billion or more of consolidated assets, Ally is required to conduct semi-annual company-run stress tests, is subject to an annual supervisory stress test conducted by the FRB, and must submit an annual capital plan to the FRB. Ally’s capital plan must include a description of all planned capital actions over a nine-quarter planning horizon. The capital plan must also include a discussion of how Ally will maintain capital above the minimum regulatory capital ratios under baseline, adverse, and severely adverse economic scenarios, and serve as a source of strength to Ally Bank. The FRB must approve Ally's capital plan before Ally may take any capital action. Even with an approved capital plan, Ally must seek the approval of the FRB before making a capital distribution if, among other factors, Ally would not meet its regulatory capital requirements after making the proposed capital distribution. As part of the 2017 Comprehensive Capital Analysis and Review (CCAR) process, on April 5, 2017, we submitted our 2017 capital plan and stress test results to the FRB. On June 23, 2017, we publicly disclosed summary results of the stress test under the most severe scenario in accordance with regulatory requirements. On June 28, 2017, we received a non-objection to our capital plan from the FRB, including the proposed capital actions contained in our submission. The capital actions included a 50% increase in the quarterly cash dividend on common stock from $0.08 per share to $0.12 per share, and a 9% increase in our share repurchase program, which has been authorized by the Ally Board of Directors, permitting us to repurchase up to $760 million of our common stock from time to time from the third quarter of 2017 through the second quarter of 2018. In addition, we submitted to the FRB the results of our company-run mid-cycle stress test conducted under multiple macroeconomic scenarios and disclosed the results of this stress test under the most severe scenario on October 5, 2017, in accordance with regulatory requirements. The following table presents information related to our common shares for each quarter since the commencement of our common share repurchase programs and initiation of a quarterly cash dividend on common stock. ($ in millions, except per share data; shares in thousands) 3rd quarter 2017 2nd quarter 2017 1st quarter 2017 4th quarter 2016 3rd quarter 2016 Common shares repurchased during period (a) Approximate dollar value $ 190 $ 204 $ 169 $ 167 $ 159 Number of shares 8,507 10,485 8,097 8,745 8,298 Number of common shares outstanding Beginning of period 452,292 462,193 467,000 475,470 483,753 End of period 443,796 452,292 462,193 467,000 475,470 Cash dividends declared per common share (b) $ 0.12 $ 0.08 $ 0.08 $ 0.08 $ 0.08 (a) Includes shares of common stock withheld to cover income taxes owed by participants in our share-based incentive plans. (b) On October 10, 2017 , the Ally Board of Directors declared a quarterly cash dividend payment of $0.12 per share on all common stock, payable on November 15, 2017 . Refer to Note 26 for further information regarding this common share dividend. Our ability to make capital distributions, including our ability to pay dividends or repurchase shares of our common stock, will continue to be subject to the FRB’s review of and non-objection to the actions that we propose each year in our annual capital plan. The amount and size of any future dividends and share repurchases will depend upon our results of operations, capital levels, future opportunities, consideration and approval by the Ally Board of Directors, and other considerations. In January 2017, the FRB finalized a rule amending the capital planning and stress testing rules, effective for the 2017 cycle. The final rule, among other things, revised the capital plan rule to no longer subject large and noncomplex firms, including Ally, to the provisions of the rule whereby the FRB may object to a capital plan on the basis of qualitative deficiencies in the firm’s capital planning process. Under the final rule, the qualitative assessment of Ally’s capital plan is conducted outside of the CCAR process, through the supervisory review process. For the 2017 cycle, the FRB's qualitative assessment of Ally's capital plan began in the third quarter of 2017. The final rule also decreased the de minimis threshold for the amount of capital that Ally could distribute to shareholders outside of an approved capital plan without seeking prior approval of the FRB, and modified Ally's reporting requirements to reduce certain reporting burdens related to capital planning and stress testing.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]	Derivative Instruments and Hedging Activities We enter into interest rate, foreign-currency, and equity swaps, futures, forwards, and options in connection with our market risk management activities. Derivative instruments are used to manage interest rate risk relating to specific groups of assets and liabilities, including available-for-sale securities, automotive loan assets, and debt. We use foreign exchange contracts to mitigate foreign-currency risk associated with foreign-currency-denominated debt, foreign exchange transactions, and our net investment in foreign subsidiaries. In addition, we also enter into equity option contracts to manage our exposure to the equity markets. Our primary objective for utilizing derivative financial instruments is to manage interest rate risk associated with our fixed- and variable-rate assets and liabilities, foreign exchange risks related to our foreign-currency denominated assets and liabilities, and market risks related to our investment portfolio and certain of our executive share-based compensation plans. Interest Rate Risk We monitor our mix of fixed- and variable-rate assets and liabilities. We may enter into interest rate swaps, forwards, futures, options, and swaptions to achieve our desired mix of fixed- and variable-rate assets and liabilities. We execute interest rate swaps, forwards, futures, and options to modify our exposure to interest rate risk by converting certain fixed-rate instruments to a variable-rate and certain variable-rate instruments to a fixed-rate. We use a mix of both derivatives that qualify for hedge accounting treatment and economic hedges. Derivatives qualifying for hedge accounting can include receive-fixed swaps designated as fair value hedges of specific fixed-rate unsecured debt obligations, receive-fixed swaps designated as fair value hedges of specific fixed-rate FHLB advances, fair value hedges of U.S. Treasury positions within our available-for-sale portfolio, and pay-fixed swaps designated as fair value hedges of specific portfolios of fixed-rate held-for-investment retail automotive loan assets. Other derivatives qualifying for hedge accounting consist of pay-fixed swaps designated as cash flow hedges of the expected future cash flows in the form of interest payments on certain variable-rate borrowings. As of September 30, 2017, there were no open hedges related to our held-for-investment retail automotive loan assets. We may also execute economic hedges, which consist of interest rate swaps and interest rate caps held to mitigate interest rate risk associated with our debt portfolio. We may also use interest rate swaps to economically hedge our net fixed-versus-variable interest rate exposure. We enter into economic hedges in the form of short-dated, exchange-traded Eurodollar futures to hedge the interest rate exposure of our fixed-rate automotive loans, as well as forwards, options, and swaptions to economically hedge our net fixed-versus-variable interest rate exposure. We also enter into interest rate lock commitments and forward-sale commitments that are executed as part of our mortgage business that meet the accounting definition of a derivative. Foreign Exchange Risk We enter into derivative financial instrument contracts to mitigate the risk associated with variability in cash flows related to our various foreign-currency exposures. We enter into foreign-currency forwards with external counterparties as net investment hedges of foreign exchange exposure on our investments in foreign subsidiaries. Our equity is impacted by the cumulative translation adjustments resulting from the translation of foreign subsidiary results; this impact is reflected in our accumulated other comprehensive loss. We also periodically enter into foreign-currency forwards to economically hedge our foreign-denominated debt, our centralized lending program, and foreign-denominated third-party loans. These foreign currency forwards that are used as economic hedges are recorded at fair value with changes recorded as income offsetting the gains and losses on the associated foreign-currency transactions. Market Risk We enter into equity options to economically hedge our exposure to the equity markets. We purchase options to assume a long position on certain equities and write options to assume a short position. Counterparty Credit Risk Derivative financial instruments contain an element of credit risk if counterparties are unable to meet the terms of the agreements. Credit risk associated with derivative financial instruments is measured as the net replacement cost should the counterparties that owe us under the contract completely fail to perform under the terms of those contracts, assuming no recoveries of underlying collateral as measured by the market value of the derivative financial instrument. To mitigate the risk of counterparty default, we maintain collateral agreements with certain counterparties. The agreements generally require both parties to post collateral in the event the fair values of the derivative financial instruments meet posting thresholds established under the agreements. In the event that either party defaults on the obligation, the secured party may seize the collateral. Generally, our collateral arrangements are bilateral such that we and the counterparty post collateral for the value of our total obligation to each other. Contractual terms provide for standard and customary exchange of collateral based on changes in the market value of the outstanding derivatives. The securing party posts additional collateral when their obligation rises or removes collateral when it falls. These payments are characterized as collateral for over-the-counter (OTC) derivatives. We execute certain derivatives such as interest rate swaps with clearinghouses, which requires us to post collateral. For these clearinghouse derivatives, these payments are recognized as settlements rather than collateral. Certain derivative instruments contain provisions that require us to either post additional collateral or immediately settle any outstanding liability balances upon the occurrence of a specified credit risk-related event. No such specified credit risk related events occurred during the third quarter of 2017 or 2016. We placed cash collateral totaling $10 million and securities collateral totaling $145 million at September 30, 2017 , and $122 million and $72 million at December 31, 2016 , respectively, in accounts maintained by counterparties. This amount primarily relates to collateral posted to support our derivative positions. This amount also excludes cash and securities pledged as collateral under repurchase agreements. At September 30, 2017 , and December 31, 2016 , we placed cash collateral totaling $10 million and $45 million , respectively, with counterparties under collateral arrangements associated with repurchase agreements. Refer to Note 14 for details on the repurchase agreements. The receivables for cash collateral placed are included on our Condensed Consolidated Balance Sheet in other assets. We received cash collateral from counterparties totaling $14 million and $10 million at September 30, 2017 , and December 31, 2016, respectively, primarily to support these derivative positions. This amount also excludes cash and securities pledged as collateral under repurchase agreements. Refer to Note 14 for details on the repurchase agreements. The payables for cash collateral received are included on our Condensed Consolidated Balance Sheet in accrued expenses and other liabilities. In certain circumstances, we receive or post securities as collateral with counterparties. We do not record collateral received on our Condensed Consolidated Balance Sheet unless certain conditions are met. At September 30, 2017 , and December 31, 2016 , we received noncash collateral of $2 million and $6 million , respectively. Included in these amounts is noncash collateral where we have been granted the right to sell or pledge the underlying assets. We have not sold or pledged any of the noncash collateral received under these agreements. Balance Sheet Presentation The following table summarizes the fair value amounts of derivative instruments reported on our Condensed Consolidated Balance Sheet . The fair value amounts are presented on a gross basis, are segregated by derivatives that are designated and qualifying as hedging instruments or those that are not, and are further segregated by type of contract within those two categories. Notional amounts are reference amounts from which contractual obligations are derived and are not recorded on the balance sheet. In our view, derivative notional is not an accurate measure of our derivative exposure when viewed in isolation from other factors, such as market rate fluctuations and counterparty credit risk. September 30, 2017 December 31, 2016 Derivative contracts in a Notional amount Derivative contracts in a Notional amount ($ in millions) receivable position (a) payable position (b) receivable position (a) payable position (b) Derivatives designated as accounting hedges Interest rate contracts Swaps (c) (d) (e) (f) (g) $ — $ — $ 6,140 $ 19 $ 21 $ 4,731 Futures (h) 1 — 60 — — — Foreign exchange contracts Forwards 3 — 176 1 — 171 Total derivatives designated as accounting hedges 4 — 6,376 20 21 4,902 Derivatives not designated as accounting hedges Interest rate contracts Swaps — — — — — 137 Futures and forwards — — 116 — — — Written options 1 30 9,452 — 73 14,518 Purchased options 30 — 9,335 73 — 14,517 Total interest rate risk 31 30 18,903 73 73 29,172 Foreign exchange contracts Futures and forwards 2 — 130 1 — 92 Total foreign exchange risk 2 — 130 1 — 92 Equity contracts Written options — — — — 1 — Purchased options — — — 1 — — Total equity risk — — — 1 1 — Total derivatives not designated as accounting hedges 33 30 19,033 75 74 29,264 Total derivatives $ 37 $ 30 $ 25,409 $ 95 $ 95 $ 34,166 (a) Derivative contracts in a receivable position are classified as other assets on the Condensed Consolidated Balance Sheet , and include accrued interest of $0 million and $7 million at September 30, 2017 , and December 31, 2016 , respectively. (b) Derivative contracts in a liability position are classified as accrued expenses and other liabilities on the Condensed Consolidated Balance Sheet , and include accrued interest of $0 million and $1 million at September 30, 2017 , and December 31, 2016 , respectively. (c) Includes fair value hedges consisting of receive-fixed swaps on fixed-rate unsecured debt obligations with $0 million and $8 million in a receivable position, $0 million and $14 million in a payable position, and a $3.1 billion and $1.7 billion notional amount at September 30, 2017 , and December 31, 2016 , respectively. The hedge notional amount of $3.1 billion at September 30, 2017 , is associated with debt maturing in approximately five or more years. (d) Includes fair value hedges consisting of receive-fixed swaps on fixed-rate secured debt obligations (FHLB advances) with $0 million and $0 million in a receivable position, $0 million and $7 million in a payable position, and a $1.6 billion and $240 million notional amount at September 30, 2017 , and December 31, 2016 , respectively. Other fair value hedges include pay-fixed swaps on portfolios of held-for-investment automotive loan assets with $0 million and $10 million in a receivable position, $0 million and $1 million in a payable position, and a $0.0 billion and $2.8 billion notional amount at September 30, 2017 , and December 31, 2016 , respectively. (e) Includes cash flow hedge of pay-fixed swap on variable-rate borrowings of a secured credit facility with $0 million in a receivable and payable position, and $1.3 billion of notional amount at September 30, 2017 . (f) Includes fair value hedge of pay-fixed swaps on fixed-rate U.S. Treasury securities with $0 million in a receivable and payable position, and $225 million of notional amount at September 30, 2017 . (g) Derivative contracts in a receivable and payable position exclude open trade equity on derivatives cleared through central clearing counterparties. Any associated collateral exchanged with our central clearing counterparties are treated as settlements of the derivative exposure, rather than collateral. Such payments are recognized as settlements of the derivatives contracts in a receivable and payable position in our Condensed Consolidated Balance Sheet. (h) Includes fair value hedge of future contract on fixed-rate U.S. Treasury securities with $1 million in a receivable position, $0 million in a payable position, and $60 million of notional amount at September 30, 2017 . Statement of Comprehensive Income Presentation The following table summarizes the location and amounts of gains and losses on derivative instruments reported in our Condensed Consolidated Statement of Comprehensive Income . Three months ended September 30, Nine months ended September 30, ( $ in millions ) 2017 2016 2017 2016 Derivatives qualifying for hedge accounting Gain (loss) recognized in earnings on derivatives Interest rate contracts Interest and fees on finance receivables and loans (a) $ — $ 16 $ 1 $ (18 ) Interest and dividends on investment securities 4 — 1 — Interest on long-term debt (b) (5 ) (31 ) 19 211 (Loss) gain recognized in earnings on hedged items Interest rate contracts Interest and fees on finance receivables and loans (c) — (17 ) (3 ) 16 Interest and dividends on investment securities (4 ) — (1 ) — Interest on long-term debt (d) 5 32 (18 ) (214 ) Total derivatives qualifying for hedge accounting — — (1 ) (5 ) Derivatives not designated as accounting hedges Gain (loss) recognized in earnings on derivatives Interest rate contracts Gain on mortgage and automotive loans, net — — 1 — Other income, net of losses — (5 ) (3 ) (2 ) Total interest rate contracts — (5 ) (2 ) (2 ) Foreign exchange contracts (e) Interest on long-term debt — — — (2 ) Other income, net of losses (3 ) (1 ) (7 ) (4 ) Total foreign exchange contracts (3 ) (1 ) (7 ) (6 ) Equity contracts Compensation and benefits expense — 2 — — Total equity contracts — 2 — — Loss recognized in earnings on derivatives $ (3 ) $ (4 ) $ (10 ) $ (13 ) (a) Amounts exclude losses related to interest for qualifying accounting hedges of retail automotive loans held-for-investment, which are primarily offset by the fixed coupon payments of the loans. The losses were $0 million and $4 million for the three months ended September 30, 2017 , and 2016 , respectively, and $1 million and $16 million for the nine months ended September 30, 2017 , and 2016 , respectively. (b) Amounts exclude gains related to interest for qualifying accounting hedges of unsecured debt, which are primarily offset by the fixed coupon payment on the long-term debt. The gains were $7 million for both the three months ended September 30, 2017 , and 2016, and $19 million and $34 million for the nine months ended September 30, 2017 , and 2016 , respectively. Amounts also exclude gains related to interest for qualifying accounting hedges of secured debt (FHLB advances), which are primarily offset by the fixed coupon payment on the long-term debt. The gains were $0 million and $1 million for the three months ended September 30, 2017 , and 2016, respectively, and $1 million and $4 million for the nine months ended September 30, 2017 , and 2016 , respectively. (c) Amounts exclude losses related to amortization of deferred loan basis adjustments on the de-designated hedged item of $6 million for both the three months ended September 30, 2017 , and 2016 , and $17 million and $15 million for the nine months ended September 30, 2017 , and 2016 , respectively. (d) Amounts exclude gains related to amortization of deferred debt basis adjustments on the de-designated hedged item of $19 million and $23 million for the three months ended September 30, 2017 , and 2016 , respectively, and $59 million and $62 million for the nine months ended September 30, 2017 , and 2016 , respectively. Amounts also exclude losses related to amortization of deferred debt basis adjustments (FHLB advances) on the de-designated hedge item of $1 million for the three months ended September 30, 2017 , and $2 million for the nine months ended September 30, 2017 . (e) Amounts exclude gains and losses related to the revaluation of the related foreign-denominated debt or receivable. Gains of $3 million and $1 million were recognized for the three months ended September 30, 2017 , and 2016 , respectively, and gains of $8 million and $4 million were recognized for the nine months ended September 30, 2017 , and 2016 , respectively. The following table summarizes derivative instruments used in cash flow and net investment hedge accounting relationships. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Cash flow hedges Interest rate contracts Gain recognized in other comprehensive loss $ 2 $ — $ 2 $ — Net investment hedges Foreign exchange contracts (Loss) gain recognized in other comprehensive loss (a) $ (6 ) $ 2 $ (12 ) $ (4 ) (a) The amounts represent the effective portion of net investment hedges. There are offsetting amounts recognized in accumulated other comprehensive loss related to the revaluation of the related net investment in foreign operations, including the tax impacts of the hedge and related net investment, as disclosed separately in Note 16 . There were gains of $7 million and losses of $2 million for the three months ended September 30, 2017 , and 2016 , respectively, and gains of $14 million and $9 million for the nine months ended September 30, 2017, and 2016.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	Income Taxes We recognized total income tax expense from continuing operations of $115 million and $350 million for the three months and nine months ended September 30, 2017 , respectively, compared to $130 million and $336 million for the same periods in 2016 . The decrease in income tax expense for the three months ended September 30, 2017 , compared to the same period in 2016 , was primarily driven by the realization of capital gains allowing for a partial release of valuation allowance. The increase in income tax expense for the nine months ended September 30, 2017 , compared to the same period in 2016 , was primarily driven by a nonrecurring tax benefit in the second quarter of 2016 due to a U.S. tax reserve release related to a prior-year federal return that reduced our liability for unrecognized tax benefits by $175 million . This benefit was partially offset by the establishment of a valuation allowance on capital loss carryforwards in the second quarter of 2016, and a decrease in pretax earnings. As of each reporting date, we consider existing evidence, both positive and negative, that could impact our view with regard to future realization of deferred tax assets. We continue to believe it is more likely than not that the benefit for certain foreign tax credits and state net operating loss carryforwards will not be realized. In recognition of this risk, we continue to provide a partial valuation allowance on the deferred tax assets relating to foreign tax credits and state net operating loss carryforwards.

Fair Value

Fair Value	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Disclosures [Text Block]	Fair Value Fair Value Measurements For purposes of this disclosure, fair value is defined as the exchange price that would be received to sell an asset or paid to transfer a liability (exit price) in the principal or most advantageous market in an orderly transaction between market participants at the measurement date under current market conditions. Fair value is based on the assumptions we believe market participants would use when pricing an asset or liability. Additionally, entities are required to consider all aspects of nonperformance risk, including the entity’s own credit standing, when measuring the fair value of a liability. GAAP specifies a three-level hierarchy that is used when measuring and disclosing fair value. The fair value hierarchy gives the highest priority to quoted prices available in active markets (i.e., observable inputs) and the lowest priority to data lacking transparency (i.e., unobservable inputs). An instrument’s categorization within the fair value hierarchy is based on the lowest level of significant input to its valuation. The following is a description of the three hierarchy levels. Level 1 Inputs are quoted prices in active markets for identical assets or liabilities at the measurement date. Additionally, the entity must have the ability to access the active market, and the quoted prices cannot be adjusted by the entity. Level 2 Inputs are other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices in active markets for similar assets or liabilities; quoted prices in inactive markets for identical or similar assets or liabilities; or inputs that are observable or can be corroborated by observable market data by correlation or other means for substantially the full term of the assets or liabilities. Level 3 Unobservable inputs are supported by little or no market activity. The unobservable inputs represent management's best assumptions of how market participants would price the assets or liabilities. Generally, Level 3 assets and liabilities are valued using pricing models, discounted cash flow methodologies, or similar techniques that require significant judgment or estimation. Transfers Transfers into or out of any hierarchy level are recognized at the end of the reporting period in which the transfer occurred. Following are descriptions of the valuation methodologies used to measure material assets and liabilities at fair value and details of the valuation models, key inputs to those models, and significant assumptions utilized. • Available-for-sale securities — All classes of available-for-sale securities are carried at fair value based on observable market prices, when available. If observable market prices are not available, our valuations are based on internally developed discounted cash flow models (an income approach) that use a market-based discount rate and consider recent market transactions, experience with similar securities, current business conditions, and analysis of the underlying collateral, as available. To estimate cash flows, we are required to utilize various significant assumptions including market observable inputs (e.g., forward interest rates) and internally developed inputs (including prepayment speeds, delinquency levels, and credit losses). • Interests retained in financial asset sales — Includes certain noncertificated interests retained from the sale of automotive finance receivables. Due to inactivity in the market, valuations are based on internally developed discounted cash flow models (an income approach) that use a market-based discount rate; therefore, we classified these assets as Level 3. The valuation considers recent market transactions, experience with similar assets, current business conditions, and analysis of the underlying collateral, as available. To estimate cash flows, we utilize various significant assumptions, including market observable inputs (e.g., forward interest rates) and internally developed inputs (e.g., prepayment speeds, delinquency levels, and credit losses). • Derivative instruments — We enter into a variety of derivative financial instruments as part of our risk management strategies. Certain of these derivatives are exchange traded, such as Eurodollar futures, options of Eurodollar futures, and equity options. To determine the fair value of these instruments, we utilize the quoted market prices for the particular derivative contracts; therefore, we classified these contracts as Level 1. We also execute OTC and centrally-cleared derivative contracts, such as interest rate swaps, swaptions, foreign-currency denominated forward contracts, prepaid equity forward contracts, caps, floors, and agency to-be-announced securities. For OTC contracts, we utilize third-party-developed valuation models that are widely accepted in the market to value these OTC derivative contracts. The specific terms of the contract and market observable inputs (such as interest rate forward curves, interpolated volatility assumptions, or equity pricing) are used in the model. We classified these OTC derivative contracts as Level 2 because all significant inputs into these models were market observable. For centrally-cleared contracts, we utilize unadjusted prices obtained from the clearing house as the basis for valuation, and they are also classified as Level 2. We also enter into interest rate lock commitments and forward-sale commitments that are executed as part of our mortgage business. These meet the accounting definition of a derivative and therefore are recorded as derivatives on our Condensed Consolidated Balance Sheet . Because these derivatives are valued using internal pricing models, they are classified as Level 3. We are required to consider all aspects of nonperformance risk, including our own credit standing, when measuring fair value of a liability. We reduce credit risk on the majority of our derivatives by entering into legally enforceable agreements that enable the posting and receiving of collateral associated with the fair value of our derivative positions on an ongoing basis. In the event that we do not enter into legally enforceable agreements that enable the posting and receiving of collateral, we will consider our credit risk and the credit risk of our counterparties in the valuation of derivative instruments through a credit valuation adjustment (CVA), if warranted. The CVA calculation utilizes the credit default swap spreads of the counterparty. Recurring Fair Value The following tables display the assets and liabilities measured at fair value on a recurring basis including financial instruments elected for the fair value option. We often economically hedge the fair value change of our assets or liabilities with derivatives and other financial instruments. The tables below display the hedges separately from the hedged items; therefore, they do not directly display the impact of our risk management activities. Recurring fair value measurements September 30, 2017 ($ in millions) Level 1 Level 2 Level 3 Total Assets Investment securities Available-for-sale securities Debt securities U.S. Treasury $ 2,073 $ — $ — $ 2,073 U.S. States and political subdivisions — 851 — 851 Foreign government 8 149 — 157 Agency mortgage-backed residential — 14,344 — 14,344 Mortgage-backed residential — 2,310 — 2,310 Mortgage-backed commercial — 509 — 509 Asset-backed — 1,039 — 1,039 Corporate debt — 1,291 — 1,291 Total debt securities 2,081 20,493 — 22,574 Equity securities (a) 525 — — 525 Total available-for-sale securities 2,606 20,493 — 23,099 Mortgage loans held-for-sale — — 9 9 Interests retained in financial asset sales — — 5 5 Derivative contracts in a receivable position Interest rate 1 30 1 32 Foreign currency — 5 — 5 Total derivative contracts in a receivable position 1 35 1 37 Total assets $ 2,607 $ 20,528 $ 15 $ 23,150 Liabilities Accrued expenses and other liabilities Derivative contracts in a payable position Interest rate $ — $ (30 ) $ — $ (30 ) Total derivative contracts in a payable position — (30 ) — (30 ) Total liabilities $ — $ (30 ) $ — $ (30 ) (a) Our investment in any one industry did not exceed 15% . Recurring fair value measurements December 31, 2016 ($ in millions) Level 1 Level 2 Level 3 Total Assets Investment securities Available-for-sale securities Debt securities U.S. Treasury $ 1,620 $ — $ — $ 1,620 U.S. States and political subdivisions — 782 — 782 Foreign government 11 151 — 162 Agency mortgage-backed residential — 10,290 — 10,290 Mortgage-backed residential — 2,097 — 2,097 Mortgage-backed commercial — 537 — 537 Asset-backed — 1,400 — 1,400 Corporate debt — 1,443 — 1,443 Total debt securities 1,631 16,700 — 18,331 Equity securities (a) 595 — — 595 Total available-for-sale securities 2,226 16,700 — 18,926 Other assets Interests retained in financial asset sales — — 29 29 Derivative contracts in a receivable position Interest rate — 92 — 92 Foreign currency — 2 — 2 Other 1 — — 1 Total derivative contracts in a receivable position 1 94 — 95 Total assets $ 2,227 $ 16,794 $ 29 $ 19,050 Liabilities Accrued expenses and other liabilities Derivative contracts in a payable position Interest rate $ — $ (94 ) $ — $ (94 ) Other (1 ) — — (1 ) Total derivative contracts in a payable position (1 ) (94 ) — (95 ) Total liabilities $ (1 ) $ (94 ) $ — $ (95 ) (a) Our investment in any one industry did not exceed 14% . The following tables present the reconciliation for all Level 3 assets and liabilities measured at fair value on a recurring basis. We often economically hedge the fair value change of our assets or liabilities with derivatives and other financial instruments. The Level 3 items presented below may be hedged by derivatives and other financial instruments that are classified as Level 1 or Level 2. Thus, the following tables do not fully reflect the impact of our risk management activities. Level 3 recurring fair value measurements Net realized/unrealized gains Fair value at September 30, 2017 Net unrealized gains included in earnings still held at September 30, 2017 ($ in millions) Fair value at July 1, 2017 included in earnings included in OCI Purchases Sales Issuances Settlements Assets Mortgage loans held-for-sale $ 3 $ 1 $ — $ 49 $ (44 ) $ — $ — $ 9 $ — Other assets Interests retained in financial asset sales 5 — — — — — — 5 — Derivative assets 1 — — — — — — 1 — Total assets $ 9 $ 1 $ — $ 49 $ (44 ) $ — $ — $ 15 $ — Level 3 recurring fair value measurements Fair value at July 1, 2016 Net realized/unrealized gains Purchases Sales Issuances Settlements Fair value at September 30, 2016 Net unrealized gains included in earnings still held at September 30, 2016 ($ in millions) included in earnings included in OCI Assets Other assets Interests retained in financial asset sales $ 31 $ 1 (a) $ — $ — $ 2 $ — $ (2 ) $ 32 $ — Total assets $ 31 $ 1 $ — $ — $ 2 $ — $ (2 ) $ 32 $ — (a) Reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income . Level 3 recurring fair value measurements Net realized/unrealized gains Fair value at September 30, 2017 Net unrealized gains included in earnings still held at September 30, 2017 ($ in millions) Fair value at Jan. 1, 2017 included in earnings included in OCI Purchases Sales Issuances Settlements Assets Mortgage loans held-for-sale $ — $ 1 $ — $ 72 $ (64 ) $ — $ — $ 9 $ — Other assets Interests retained in financial asset sales 29 1 — — 8 — (33 ) 5 — Derivative assets — 1 — — — — — 1 1 Total assets $ 29 $ 3 $ — $ 72 $ (56 ) $ — $ (33 ) $ 15 $ 1 Level 3 recurring fair value measurements Fair value at Jan. 1, 2016 Net realized/unrealized gains Purchases Sales Issuances Settlements Fair value at September 30, 2016 Net unrealized gains included in earnings still held at September 30, 2016 ($ in millions) included in earnings included in OCI Assets Other assets Interests retained in financial asset sales $ 40 $ 4 (a) $ — $ — $ 8 $ — $ (20 ) $ 32 $ — Total assets $ 40 $ 4 $ — $ — $ 8 $ — $ (20 ) $ 32 $ — (a) Reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income . Nonrecurring Fair Value We may be required to measure certain assets and liabilities at fair value from time to time. These periodic fair value measures typically result from the application of lower-of-cost or fair value accounting or certain impairment measures. These items would constitute nonrecurring fair value measures. The following tables display the assets and liabilities measured at fair value on a nonrecurring basis. Nonrecurring fair value measurements Lower-of-cost or fair value or valuation reserve allowance Total gain (loss) included in earnings for the three months ended Total gain (loss) included in earnings for the nine months ended September 30, 2017 ($ in millions) Level 1 Level 2 Level 3 Total Assets Loans held-for-sale, net $ — $ — $ 9 $ 9 $ — n/m (a) n/m (a) Commercial finance receivables and loans, net (b) Automotive — — 29 29 $ (4 ) n/m (a) n/m (a) Other — — 35 35 (16 ) n/m (a) n/m (a) Total commercial finance receivables and loans, net — — 64 64 (20 ) n/m (a) n/m (a) Other assets Repossessed and foreclosed assets (c) — — 13 13 (2 ) n/m (a) n/m (a) Other — — 3 3 — n/m (a) n/m (a) Total assets $ — $ — $ 89 $ 89 $ (22 ) n/m n/m n/m = not meaningful (a) We consider the applicable valuation or loan loss allowance to be the most relevant indicator of the impact on earnings caused by the fair value measurement. Accordingly, the table above excludes total gains and losses included in earnings for these items. The carrying values are inclusive of the respective valuation or loan loss allowance. (b) Represents the portion of the portfolio specifically impaired during 2017. The related valuation allowance represents the cumulative adjustment to fair value of those specific receivables. (c) The allowance provided for repossessed and foreclosed assets represents any cumulative valuation adjustment recognized to adjust the assets to fair value. Nonrecurring fair value measurements Lower-of-cost or fair value or valuation reserve allowance Total gain included in earnings for the three months ended Total gain included in earnings for the nine months ended September 30, 2016 ($ in millions) Level 1 Level 2 Level 3 Total Assets Loans held-for-sale, net $ — $ — $ 56 $ 56 $ — n/m (a) n/m (a) Commercial finance receivables and loans, net (b) Commercial and industrial Automotive — — 30 30 (7 ) n/m (a) n/m (a) Other — — 45 45 (17 ) n/m (a) n/m (a) Total commercial finance receivables and loans, net — — 75 75 (24 ) n/m (a) n/m (a) Other assets Repossessed and foreclosed assets (c) — — 15 15 (4 ) n/m (a) n/m (a) Other — — 7 7 — n/m (a) n/m (a) Total assets $ — $ — $ 153 $ 153 $ (28 ) n/m n/m n/m = not meaningful (a) We consider the applicable valuation or loan loss allowance to be the most relevant indicator of the impact on earnings caused by the fair value measurement. Accordingly, the table above excludes total gains and losses included in earnings for these items. The carrying values are inclusive of the respective valuation or loan loss allowance. (b) Represents the portion of the portfolio specifically impaired during 2016 . The related valuation allowance represents the cumulative adjustment to fair value of those specific receivables. (c) The allowance provided for repossessed and foreclosed assets represents any cumulative valuation adjustment recognized to adjust the assets to fair value. Fair Value Option for Financial Assets We elected the fair value option for an insignificant amount of conforming mortgage loans held-for-sale. We elected the fair value option to mitigate earnings volatility by better matching the accounting for the assets with the related hedges. Our intent in electing fair value measurement was to mitigate a divergence between accounting losses and economic exposure for certain assets and liabilities. Fair Value of Financial Instruments The following table presents the carrying and estimated fair value of financial instruments, except for those recorded at fair value on a recurring basis presented in the previous section of this note titled Recurring Fair Value. When possible, we use quoted market prices to determine fair value. Where quoted market prices are not available, the fair value is internally derived based on appropriate valuation methodologies with respect to the amount and timing of future cash flows and estimated discount rates. However, considerable judgment is required in interpreting current market data to develop the market assumptions and inputs necessary to estimate fair value. As such, the actual amount received to sell an asset or the amount paid to settle a liability could differ from our estimates. Fair value information presented herein was based on information available at September 30, 2017 , and December 31, 2016 . Estimated fair value ($ in millions) Carrying value Level 1 Level 2 Level 3 Total September 30, 2017 Financial assets Held-to-maturity securities $ 1,839 $ — $ 1,807 $ — $ 1,807 Loans held-for-sale, net 9 — — 9 9 Finance receivables and loans, net 117,585 — — 119,498 119,498 Nonmarketable equity investments (a) 1,053 — 1,026 26 1,052 Financial liabilities Deposit liabilities $ 90,116 $ — $ — $ 88,151 $ 88,151 Short-term borrowings 10,175 — — 10,177 10,177 Long-term debt 45,122 — 29,776 17,880 47,656 December 31, 2016 Financial assets Held-to-maturity securities $ 839 $ — $ 789 $ — $ 789 Finance receivables and loans, net 117,800 — — 118,750 118,750 Nonmarketable equity investments 1,046 — 1,012 55 1,067 Financial liabilities Deposit liabilities $ 79,022 $ — $ — $ 78,469 $ 78,469 Short-term borrowings 12,673 — — 12,675 12,675 Long-term debt 54,128 — 22,036 34,084 56,120 (a) Excludes investments with a carrying value of $12 million and fair value of $35 million at September 30, 2017 , for which fair value is measured at net asset value (or its equivalent) as a practical expedient. The following describes the methodologies and assumptions used to determine fair value for the significant classes of financial instruments. In addition to the valuation methods discussed below, we also followed guidelines for determining whether a market was not active and a transaction was not distressed. We assumed the price that would be received in an orderly transaction (including a market-based return) and not in forced liquidation or distressed sale. • Cash and cash equivalents — Included in cash and cash equivalents are highly liquid investments that are readily convertible to known amounts of cash and which are subject to an insignificant risk of change in value due to interest rate, quoted price, or penalty on withdrawal. Classified as Level 1 under the fair value hierarchy, cash and cash equivalents generally expose us to limited credit risk and are so near maturity that they present insignificant risk of changes in value because of changes in interest rates. Accordingly, the carrying value approximates the fair value of these instruments. • Held-to-maturity securities — Held-to-maturity securities, which consist of asset-backed retained notes and residential mortgage-backed debt securities issued by government agencies, are carried at amortized cost. For fair value disclosure purposes, held-to-maturity securities are classified as Level 2, with fair value based on observable market prices, when available. • Finance receivables and loans, net — With the exception of mortgage loans held-for-investment, the fair value of finance receivables and loans was based on discounted future cash flows using applicable spreads to approximate current rates applicable to each category of finance receivables and loans (an income approach using Level 3 inputs). The carrying value of commercial receivables in certain markets and certain automotive and other receivables for which interest rates reset on a short-term basis with applicable market indices are assumed to approximate fair value either because of the short-term nature or because of the interest rate adjustment feature. The fair value of commercial receivables in other markets was based on discounted future cash flows using applicable spreads to approximate current rates applicable to similar assets in those markets. The fair value of mortgage loans held-for-investment was based on a discounted cash flow basis utilizing cash flow projections from models that utilized prepayment, default, and discount rate assumptions. These valuations consider unique attributes of the loans such as geography, delinquency status, product type, and other factors. • Nonmarketable equity investments — Nonmarketable equity investments primarily include investments in FHLB and FRB stock and other equity investments carried at cost. As a member of the FHLB and FRB, Ally Bank is required to hold FHLB and FRB stock. The stock can be sold only to the FHLB and FRB upon termination of membership, or redeemed at the sole discretion of the FHLB and FRB, respectively. The fair value of FHLB and FRB stock is equal to the stock’s par value since the stock is bought, sold, and/or redeemed at par. FHLB and FRB stock is carried at cost, which generally represents the stock’s par value. • Deposit liabilities — Deposit liabilities represent certain consumer and brokered bank deposits, mortgage escrow deposits, and dealer deposits. The fair value of deposits at Level 3 was estimated by discounting projected cash flows based on discount factors derived from the forward interest rate swap curve. • Short-term borrowings and Long-term debt — Level 2 debt was valued using quoted market prices for similar instruments, when available, or other means for substantiation with observable inputs. Debt valued by discounting projected cash flows using internally derived inputs, such as prepayment speeds and discount rates, was classified as Level 3. For our credit facilities, which are floating rate in nature and where pricing occurs on a more frequent basis, the carrying amount or par value is considered to be a reasonable estimate of fair value. As of June 30, 2017, we began using quoted market prices of similar instruments for certain of our long-term debt associated with asset-backed securitizations for which observable market information exists. As a result, the corresponding financial instruments have been transferred from Level 3 to Level 2 within the fair value hierarchy following the change in valuation technique driven by the availability of an independent pricing service. • Financial instruments for which carrying value approximates fair value — Certain financial instruments that are not carried at fair value on the consolidated balance sheet are carried at amounts that approximate fair value primarily due to their short term nature and limited credit risk. These instruments include restricted cash, cash collateral, accrued interest receivable, accrued interest payable, trade receivables and payables, and other short term receivables and payables.

Offsetting Assets and Liabiliti

Offsetting Assets and Liabilities Offsetting Assets and Liabilities	9 Months Ended
	Sep. 30, 2017
Offsetting Assets and Liabilities [Abstract]
Offsetting Assets and Liabilities [Text Block]	Offsetting Assets and Liabilities Our derivative contracts and repurchase/reverse repurchase transactions are supported by qualifying master netting and master repurchase agreements. These agreements are legally enforceable bilateral agreements that (1) create a single legal obligation for all individual transactions covered by the agreement to the nondefaulting entity upon an event of default of the counterparty, including bankruptcy, insolvency, or similar proceeding, and (2) provide the nondefaulting entity the right to accelerate, terminate, and close-out on a net basis all transactions under the agreement and to liquidate or set off collateral promptly upon an event of default of the counterparty. To further mitigate the risk of counterparty default related to derivative instruments, we maintain collateral agreements with certain counterparties. The agreements require both parties to maintain collateral in the event the fair values of the derivative financial instruments meet established thresholds. In the event that either party defaults on the obligation, the secured party may seize the collateral. Generally, our collateral arrangements are bilateral such that we and the counterparty post collateral for the obligation. Contractual terms provide for standard and customary exchange of collateral based on changes in the market value of the outstanding derivatives. A party posts additional collateral when their obligation rises or removes collateral when it falls, such that the net replacement cost of the nondefaulting party is covered in the event of counterparty default. In certain instances as it relates to our derivative instruments, we have the option to report derivative assets and liabilities as well as assets and liabilities associated with cash collateral received or delivered that is governed by a master netting agreement on a net basis as long as certain qualifying criteria are met. Similarly, for our repurchase/reverse repurchase transactions, we have the option to report recognized assets and liabilities subject to a master netting agreement on a net basis if certain qualifying criteria are met. At September 30, 2017 , these instruments are reported as gross assets and gross liabilities on the Condensed Consolidated Balance Sheet . The composition of offsetting derivative instruments, financial assets, and financial liabilities was as follows. Gross amounts of recognized assets/(liabilities) Gross amounts offset in the Condensed Consolidated Balance Sheet Net amounts of assets/(liabilities) presented in the Condensed Consolidated Balance Sheet Gross amounts not offset in the Condensed Consolidated Balance Sheet September 30, 2017 ($ in millions) Financial instruments Collateral (a) (b) (c) Net amount Assets Derivative assets in net asset positions $ 36 $ — $ 36 $ — $ (4 ) $ 32 Derivative assets in net liability positions — — — — — — Derivative assets with no offsetting arrangements 1 — 1 — — 1 Total assets (d) $ 37 $ — $ 37 $ — $ (4 ) $ 33 Liabilities Derivative liabilities in net liability positions $ (30 ) $ — $ (30 ) $ — $ — $ (30 ) Derivative liabilities in net asset positions — — — — — — Total derivative liabilities (d) (30 ) — (30 ) — — (30 ) Securities sold under agreements to repurchase (e) (1,171 ) — (1,171 ) — 1,171 — Total liabilities $ (1,201 ) $ — $ (1,201 ) $ — $ 1,171 $ (30 ) (a) Financial collateral received/pledged shown as a balance based on the sum of all net asset and liability positions between Ally and each individual derivative counterparty. (b) Amounts disclosed are limited to the financial asset or liability balance and, accordingly, exclude excess collateral received or pledged and noncash collateral received. $2 million of noncash derivative collateral pledged to us was excluded at September 30, 2017 . We do not record such collateral received on our Condensed Consolidated Balance Sheet unless certain conditions are met. (c) Certain agreements grant us the right to sell or pledge the noncash assets we receive as collateral. Noncash collateral pledged to us where the agreement grants us the right to sell or pledge the underlying assets had a fair value of $2 million at September 30, 2017 . We have not sold or pledged any of the noncash collateral received under these agreements as of September 30, 2017 . (d) For additional information on derivative instruments and hedging activities, refer to Note 19 . (e) For additional information on securities sold under agreements to repurchase, refer to Note 14 . Gross amounts of recognized assets/(liabilities) Gross amounts offset in the Condensed Consolidated Balance Sheet Net amounts of assets/(liabilities) presented in the Condensed Consolidated Balance Sheet Gross amounts not offset in the Condensed Consolidated Balance Sheet December 31, 2016 ($ in millions) Financial instruments Collateral (a) (b) (c) Net amount Assets Derivative assets in net asset positions $ 87 $ — $ 87 $ (4 ) $ (9 ) $ 74 Derivative assets in net liability positions 8 — 8 (8 ) — — Total assets (d) $ 95 $ — $ 95 $ (12 ) $ (9 ) $ 74 Liabilities Derivative liabilities in net liability positions $ (91 ) $ — $ (91 ) $ 8 $ 13 $ (70 ) Derivative liabilities in net asset positions (4 ) — (4 ) 4 — — Total derivative liabilities (d) (95 ) — (95 ) 12 13 (70 ) Securities sold under agreements to repurchase (e) (676 ) — (676 ) — 676 — Total liabilities $ (771 ) $ — $ (771 ) $ 12 $ 689 $ (70 ) (a) Financial collateral received/pledged shown as a balance based on the sum of all net asset and liability positions between Ally and each individual derivative counterparty. (b) Amounts disclosed are limited to the financial asset or liability balance and, accordingly, exclude excess collateral received or pledged and noncash collateral received. $6 million of noncash derivative collateral pledged to us was excluded at December 31, 2016. We do not record such collateral received on our Condensed Consolidated Balance Sheet unless certain conditions are met. (c) Certain agreements grant us the right to sell or pledge the noncash assets we receive as collateral. Noncash collateral pledged to us where the agreement grants us the right to sell or pledge the underlying assets had a fair value of $6 million at December 31, 2016. We have not sold or pledged any of the noncash collateral received under these agreements as of December 31, 2016. (d) For additional information on derivative instruments and hedging activities, refer to Note 19 . (e) For additional information on securities sold under agreements to repurchase, refer to Note 14 .

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Segment Reporting Disclosure [Text Block]	Segment Information Operating segments are defined as components of an enterprise that engage in business activity from which revenues are earned and expenses incurred for which discrete financial information is available that is evaluated regularly by our chief operating decision maker in deciding how to allocate resources and in assessing performance. We report our results of operations on a line-of-business basis through four operating segments: Automotive Finance operations, Insurance operations, Mortgage Finance operations, and Corporate Finance operations, with the remaining activity reported in Corporate and Other. The operating segments are determined based on the products and services offered, and reflect the manner in which financial information is currently evaluated by management. The following is a description of each of our reportable operating segments. Automotive Finance operations — One of the largest full service automotive finance operations in the U.S. providing automotive financing services to consumers and automotive dealers, and automotive and equipment financing services to companies and municipalities. Our automotive finance services include providing retail installment sales contracts, loans and leases, offering term loans to dealers, financing dealer floorplans and other lines of credit to dealers, warehouse lines to companies, fleet financing, providing financing to companies and municipalities for the purchase or lease of vehicles and equipment, and vehicle remarketing services. Insurance operations — A complementary automotive-focused business offering both consumer finance protection and insurance products sold primarily through the automotive dealer channel, and commercial insurance products sold directly to dealers. As part of our focus on offering dealers a broad range of consumer financial and insurance products, we provide vehicle service contracts, vehicle maintenance contracts, and guaranteed asset protection products. We also underwrite select commercial insurance coverages, which primarily insure dealers' wholesale vehicle inventory. Mortgage Finance operations — Primarily consists of the management of a held-for-investment consumer mortgage finance loan portfolio, which includes bulk purchases of high-quality jumbo and low-to-moderate income (LMI) mortgage loans originated by third parties. In late 2016, we introduced our direct-to-consumer mortgage offering, named Ally Home, consisting of a variety of jumbo and conforming fixed- and adjustable-rate mortgage products through a third-party fulfillment partner. Under our current arrangement, conforming mortgages are originated as held-for-sale and sold, while jumbo mortgages are originated as held-for-investment. Servicing is performed by a third party and no mortgage servicing rights are created. Corporate Finance operations — Primarily provides senior secured leveraged cash flow and asset-based loans to mostly U.S.-based middle market companies. Our primary focus is on businesses owned by private equity sponsors with loans typically used for leveraged buyouts, mergers and acquisitions, debt refinancing, restructurings, and working capital. In 2017, we introduced a commercial real estate product to serve companies in the healthcare industry. Corporate and Other primarily consists of activity related to centralized corporate treasury activities such as management of the cash and corporate investment securities and loan portfolios, short- and long-term debt, retail and brokered deposit liabilities, derivative instruments, the amortization of the discount associated with debt issuances, and the residual impacts of our corporate funds-transfer pricing (FTP) and treasury asset liability management (ALM) activities. Corporate and Other also includes certain equity investments, which primarily consist of FHLB and FRB stock, the management of our legacy mortgage portfolio, which primarily consists of loans originated prior to January 1, 2009, and reclassifications and eliminations between the reportable operating segments. Additionally, financial results related to Ally Invest are currently included within Corporate and Other. We utilize an FTP methodology for the majority of our business operations. The FTP methodology assigns charge rates and credit rates to classes of assets and liabilities based on expected duration and the benchmark rate curve plus an assumed credit spread. Matching duration allocates interest income and interest expense to these reportable segments so their respective results are insulated from interest rate risk. This methodology is consistent with our ALM practices, which includes managing interest rate risk centrally at a corporate level. The net residual impact of the FTP methodology is included within the results of Corporate and Other. The information presented in our reportable operating segments is based in part on internal allocations, which involve management judgment. Financial information for our reportable operating segments is summarized as follows. Three months ended September 30, ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated (a) 2017 Net financing revenue and other interest income $ 950 $ 15 $ 32 $ 39 $ 45 $ 1,081 Other revenue 82 272 2 5 20 381 Total net revenue 1,032 287 34 44 65 1,462 Provision for loan losses 312 — 4 3 (5 ) 314 Total noninterest expense 420 218 28 19 68 753 Income from continuing operations before income tax expense $ 300 $ 69 $ 2 $ 22 $ 2 $ 395 Total assets $ 112,141 $ 7,432 $ 9,804 $ 3,699 $ 30,937 $ 164,013 2016 Net financing revenue and other interest income (loss) $ 933 $ 14 $ 25 $ 30 $ (6 ) $ 996 Other revenue 74 264 — 4 46 388 Total net revenue 1,007 278 25 34 40 1,384 Provision for loan losses 270 — 1 3 (16 ) 258 Total noninterest expense 418 222 16 16 63 735 Income (loss) from continuing operations before income tax expense $ 319 $ 56 $ 8 $ 15 $ (7 ) $ 391 Total assets $ 113,669 $ 7,259 $ 7,933 $ 3,232 $ 25,304 $ 157,397 (a) Net financing revenue and other interest income after the provision for loan losses totaled $767 million and $738 million for the three months ended September 30, 2017 , and 2016 , respectively. Nine months ended September 30, ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated (a) 2017 Net financing revenue and other interest income $ 2,774 $ 44 $ 98 $ 121 $ 90 $ 3,127 Other revenue 290 781 3 33 58 1,165 Total net revenue 3,064 825 101 154 148 4,292 Provision for loan losses 846 — 6 15 (13 ) 854 Total noninterest expense 1,283 737 77 57 187 2,341 Income (loss) from continuing operations before income tax expense $ 935 $ 88 $ 18 $ 82 $ (26 ) $ 1,097 Total assets $ 112,141 $ 7,432 $ 9,804 $ 3,699 $ 30,937 $ 164,013 2016 Net financing revenue and other interest income (loss) $ 2,758 $ 44 $ 71 $ 87 $ (29 ) $ 2,931 Other revenue 228 777 — 14 119 1,138 Total net revenue 2,986 821 71 101 90 4,069 Provision for loan losses 649 — 4 12 (15 ) 650 Total noninterest expense 1,255 733 48 49 133 2,218 Income (loss) from continuing operations before income tax expense $ 1,082 $ 88 $ 19 $ 40 $ (28 ) $ 1,201 Total assets $ 113,669 $ 7,259 $ 7,933 $ 3,232 $ 25,304 $ 157,397 (a) Net financing revenue and other interest income after the provision for loan losses totaled $2,273 million and $2,281 million for the nine months ended September 30, 2017 , and 2016 , respectively.

Parent and Guarantor Condensed

Parent and Guarantor Condensed Consolidating Financial Statements	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Condensed Financial Statements [Text Block]	Parent and Guarantor Condensed Consolidating Financial Statements Certain of our senior notes issued by the parent are guaranteed by 100% directly owned subsidiaries of Ally (the Guarantors). As of September 30, 2017 , the Guarantors include Ally US LLC and IB Finance Holding Company, LLC (IB Finance), each of which fully and unconditionally guarantee the senior notes on a joint and several basis. The following financial statements present condensed consolidating financial data for (i) Ally Financial Inc. (on a parent company-only basis); (ii) the Guarantors; (iii) the nonguarantor subsidiaries (all other subsidiaries); and (iv) an elimination column for adjustments to arrive at (v) the information for the parent company, the Guarantors, and nonguarantors on a consolidated basis. Investments in subsidiaries are accounted for by the parent company and the Guarantors using the equity-method for this presentation. Results of operations of subsidiaries are therefore classified in the parent company’s and Guarantors’ investment in subsidiaries accounts. The elimination entries set forth in the following condensed consolidating financial statements eliminate distributed and undistributed income of subsidiaries, investments in subsidiaries, and intercompany balances and transactions between the parent, the Guarantors, and nonguarantors. Condensed Consolidating Statements of Comprehensive Income Three months ended September 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing revenue and other interest income Interest and fees on finance receivables and loans $ 13 $ — $ 1,473 $ — $ 1,486 Interest and fees on finance receivables and loans — intercompany 2 — 1 (3 ) — Interest and dividends on investment securities and other earning assets — — 157 — 157 Interest on cash and cash equivalents 2 — 9 — 11 Interest-bearing cash — intercompany 1 — 2 (3 ) — Operating leases 3 — 431 — 434 Total financing revenue and other interest income 21 — 2,073 (6 ) 2,088 Interest expense Interest on deposits — — 286 (1 ) 285 Interest on short-term borrowings 16 — 18 — 34 Interest on long-term debt 278 — 138 — 416 Interest on intercompany debt 3 — 2 (5 ) — Total interest expense 297 — 444 (6 ) 735 Net depreciation expense on operating lease assets 3 — 269 — 272 Net financing revenue (279 ) — 1,360 — 1,081 Cash dividends from subsidiaries Bank subsidiary 2,900 2,900 — (5,800 ) — Nonbank subsidiaries 101 — — (101 ) — Other revenue Insurance premiums and service revenue earned — — 252 — 252 Gain on mortgage and automotive loans, net 9 — 6 — 15 Loss on extinguishment of debt (1 ) — (3 ) — (4 ) Other gain on investments, net — — 23 — 23 Other income, net of losses 138 — 199 (242 ) 95 Total other revenue 146 — 477 (242 ) 381 Total net revenue 2,868 2,900 1,837 (6,143 ) 1,462 Provision for loan losses 161 — 153 — 314 Noninterest expense Compensation and benefits expense 17 — 247 — 264 Insurance losses and loss adjustment expenses — — 65 — 65 Other operating expenses 208 — 459 (243 ) 424 Total noninterest expense 225 — 771 (243 ) 753 Income from continuing operations before income tax (benefit) expense and undistributed (loss) income of subsidiaries 2,482 2,900 913 (5,900 ) 395 Income tax (benefit) expense from continuing operations (135 ) — 250 — 115 Net income from continuing operations 2,617 2,900 663 (5,900 ) 280 Income (loss) from discontinued operations, net of tax 4 — (2 ) — 2 Undistributed (loss) income of subsidiaries Bank subsidiary (2,524 ) (2,524 ) — 5,048 — Nonbank subsidiaries 185 — — (185 ) — Net income 282 376 661 (1,037 ) 282 Other comprehensive income, net of tax 48 36 51 (87 ) 48 Comprehensive income $ 330 $ 412 $ 712 $ (1,124 ) $ 330 Three months ended September 30, 2016 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing (loss) revenue and other interest income Interest and fees on finance receivables and loans $ (15 ) $ — $ 1,322 $ — $ 1,307 Interest and fees on finance receivables and loans — intercompany 2 — 2 (4 ) — Interest and dividends on investment securities and other earning assets — — 102 (1 ) 101 Interest on cash and cash equivalents 1 — 2 — 3 Interest-bearing cash — intercompany — — 2 (2 ) — Operating leases 4 — 645 — 649 Total financing (loss) revenue and other interest income (8 ) — 2,075 (7 ) 2,060 Interest expense Interest on deposits 2 — 210 — 212 Interest on short-term borrowings 10 — 4 — 14 Interest on long-term debt 289 — 141 — 430 Interest on intercompany debt 5 — 2 (7 ) — Total interest expense 306 — 357 (7 ) 656 Net depreciation expense on operating lease assets 3 — 405 — 408 Net financing revenue (317 ) — 1,313 — 996 Cash dividends from subsidiaries Nonbank subsidiaries 170 — — (170 ) — Other revenue Insurance premiums and service revenue earned — — 238 — 238 (Loss) gain on mortgage and automotive loans, net (7 ) — 7 — — Other gain on investments, net — — 52 — 52 Other income, net of losses 298 — 231 (431 ) 98 Total other revenue 291 — 528 (431 ) 388 Total net revenue 144 — 1,841 (601 ) 1,384 Provision for loan losses 147 — 111 — 258 Noninterest expense Compensation and benefits expense 143 — 105 — 248 Insurance losses and loss adjustment expenses — — 69 — 69 Other operating expenses 307 — 541 (430 ) 418 Total noninterest expense 450 — 715 (430 ) 735 (Loss) income from continuing operations before income tax (benefit) expense and undistributed income of subsidiaries (453 ) — 1,015 (171 ) 391 Income tax (benefit) expense from continuing operations (88 ) — 218 — 130 Net (loss) income from continuing operations (365 ) — 797 (171 ) 261 Loss from discontinued operations, net of tax (47 ) — (5 ) — (52 ) Undistributed income of subsidiaries Bank subsidiary 325 325 — (650 ) — Nonbank subsidiaries 296 — — (296 ) — Net income 209 325 792 (1,117 ) 209 Other comprehensive loss, net of tax (4 ) (3 ) (9 ) 12 (4 ) Comprehensive income $ 205 $ 322 $ 783 $ (1,105 ) $ 205 Nine months ended September 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing (loss) revenue and other interest income Interest and fees on finance receivables and loans $ (57 ) $ — $ 4,358 $ — $ 4,301 Interest and fees on finance receivables and loans — intercompany 10 — 5 (15 ) — Interest and dividends on investment securities and other earning assets — — 439 (2 ) 437 Interest on cash and cash equivalents 6 — 17 — 23 Interest-bearing cash — intercompany 1 — 5 (6 ) — Operating leases 9 — 1,456 — 1,465 Total financing (loss) revenue and other interest income (31 ) — 6,280 (23 ) 6,226 Interest expense Interest on deposits 2 — 765 (1 ) 766 Interest on short-term borrowings 52 — 42 — 94 Interest on long-term debt 834 — 423 — 1,257 Interest on intercompany debt 12 — 10 (22 ) — Total interest expense 900 — 1,240 (23 ) 2,117 Net depreciation expense on operating lease assets 8 — 974 — 982 Net financing revenue (939 ) — 4,066 — 3,127 Cash dividends from subsidiaries Bank subsidiary 2,900 2,900 — (5,800 ) — Nonbank subsidiaries 528 — — (528 ) — Other revenue Insurance premiums and service revenue earned — — 720 — 720 Gain on mortgage and automotive loans, net 39 — 26 — 65 Loss on extinguishment of debt (1 ) — (5 ) — (6 ) Other gain on investments, net — — 73 — 73 Other income, net of losses 569 — 635 (891 ) 313 Total other revenue 607 — 1,449 (891 ) 1,165 Total net revenue 3,096 2,900 5,515 (7,219 ) 4,292 Provision for loan losses 350 — 504 — 854 Noninterest expense Compensation and benefits expense 157 — 657 — 814 Insurance losses and loss adjustment expenses — — 278 — 278 Other operating expenses 709 — 1,431 (891 ) 1,249 Total noninterest expense 866 — 2,366 (891 ) 2,341 Income from continuing operations before income tax (benefit) expense and undistributed (loss) income of subsidiaries 1,880 2,900 2,645 (6,328 ) 1,097 Income tax (benefit) expense from continuing operations (362 ) — 712 — 350 Net income from continuing operations 2,242 2,900 1,933 (6,328 ) 747 Income (loss) from discontinued operations, net of tax 6 — (5 ) — 1 Undistributed (loss) income of subsidiaries Bank subsidiary (1,760 ) (1,760 ) — 3,520 — Nonbank subsidiaries 260 — — (260 ) — Net income 748 1,140 1,928 (3,068 ) 748 Other comprehensive income, net of tax 144 91 140 (231 ) 144 Comprehensive income $ 892 $ 1,231 $ 2,068 $ (3,299 ) $ 892 Nine months ended September 30, 2016 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing (loss) revenue and other interest income Interest and fees on finance receivables and loans $ (82 ) $ — $ 3,889 $ — $ 3,807 Interest and fees on finance receivables and loans — intercompany 8 — 6 (14 ) — Interest and dividends on investment securities and other earning assets — — 303 (1 ) 302 Interest on cash and cash equivalents 4 — 6 — 10 Interest-bearing cash — intercompany — — 7 (7 ) — Operating leases 14 — 2,105 — 2,119 Total financing (loss) revenue and other interest income (56 ) — 6,316 (22 ) 6,238 Interest expense Interest on deposits 6 — 602 — 608 Interest on short-term borrowings 31 — 8 — 39 Interest on long-term debt 868 — 440 — 1,308 Interest on intercompany debt 14 — 8 (22 ) — Total interest expense 919 — 1,058 (22 ) 1,955 Net depreciation expense on operating lease assets 11 — 1,341 — 1,352 Net financing revenue (986 ) — 3,917 — 2,931 Cash dividends from subsidiaries Nonbank subsidiaries 800 — — (800 ) — Other revenue Insurance premiums and service revenue earned — — 704 — 704 (Loss) gain on mortgage and automotive loans, net (11 ) — 15 — 4 Loss on extinguishment of debt (2 ) — (2 ) — (4 ) Other gain on investments, net — — 145 — 145 Other income, net of losses 989 — 661 (1,361 ) 289 Total other revenue 976 — 1,523 (1,361 ) 1,138 Total net revenue 790 — 5,440 (2,161 ) 4,069 Provision for loan losses 295 — 355 — 650 Noninterest expense Compensation and benefits expense 430 — 312 — 742 Insurance losses and loss adjustment expenses — — 287 — 287 Other operating expenses 963 — 1,586 (1,360 ) 1,189 Total noninterest expense 1,393 — 2,185 (1,360 ) 2,218 (Loss) income from continuing operations before income tax (benefit) expense and undistributed income (loss) of subsidiaries (898 ) — 2,900 (801 ) 1,201 Income tax (benefit) expense from continuing operations (196 ) (82 ) 614 — 336 Net (loss) income from continuing operations (702 ) 82 2,286 (801 ) 865 Loss from discontinued operations, net of tax (39 ) — (7 ) — (46 ) Undistributed income (loss) of subsidiaries Bank subsidiary 932 932 — (1,864 ) — Nonbank subsidiaries 628 (2 ) — (626 ) — Net income 819 1,012 2,279 (3,291 ) 819 Other comprehensive income, net of tax 262 143 234 (377 ) 262 Comprehensive income $ 1,081 $ 1,155 $ 2,513 $ (3,668 ) $ 1,081 Condensed Consolidating Balance Sheet September 30, 2017 ($ in millions) Parent (a) Guarantors Nonguarantors (a) Consolidating adjustments Ally consolidated Assets Cash and cash equivalents Noninterest-bearing $ 74 $ — $ 736 $ — $ 810 Interest-bearing 5 — 3,609 — 3,614 Interest-bearing — intercompany 1,495 — 558 (2,053 ) — Total cash and cash equivalents 1,574 — 4,903 (2,053 ) 4,424 Available-for-sale securities — — 23,099 — 23,099 Held-to-maturity securities — — 1,923 (84 ) 1,839 Loans held-for-sale, net — — 18 — 18 Finance receivables and loans, net Finance receivables and loans, net 7,694 — 111,177 — 118,871 Intercompany loans to Nonbank subsidiaries 788 — 394 (1,182 ) — Allowance for loan losses (197 ) — (1,089 ) — (1,286 ) Total finance receivables and loans, net 8,285 — 110,482 (1,182 ) 117,585 Investment in operating leases, net 23 — 8,908 — 8,931 Intercompany receivables from Bank subsidiary 59 — — (59 ) — Nonbank subsidiaries 76 — 91 (167 ) — Investment in subsidiaries Bank subsidiary 16,383 16,383 — (32,766 ) — Nonbank subsidiaries 9,045 — — (9,045 ) — Premiums receivable and other insurance assets — — 2,085 (31 ) 2,054 Other assets 3,174 — 4,910 (2,021 ) 6,063 Total assets $ 38,619 $ 16,383 $ 156,419 $ (47,408 ) $ 164,013 Liabilities Deposit liabilities Noninterest-bearing $ — $ — $ 129 $ — $ 129 Interest-bearing 14 — 89,973 — 89,987 Interest-bearing — intercompany — — 1,495 (1,495 ) — Total deposit liabilities 14 — 91,597 (1,495 ) 90,116 Short-term borrowings 3,379 — 6,796 — 10,175 Long-term debt 19,969 — 25,153 — 45,122 Intercompany debt to Bank subsidiary 84 — — (84 ) — Nonbank subsidiaries 952 — 788 (1,740 ) — Intercompany payables to Nonbank subsidiaries 149 — 108 (257 ) — Interest payable 278 — 274 — 552 Unearned insurance premiums and service revenue — — 2,583 — 2,583 Accrued expenses and other liabilities 221 — 3,692 (2,021 ) 1,892 Total liabilities 25,046 — 130,991 (5,597 ) 150,440 Total equity 13,573 16,383 25,428 (41,811 ) 13,573 Total liabilities and equity $ 38,619 $ 16,383 $ 156,419 $ (47,408 ) $ 164,013 (a) Amounts presented are based upon the legal transfer of the underlying assets to VIEs in order to reflect legal ownership. December 31, 2016 ($ in millions) Parent (a) Guarantors Nonguarantors (a) Consolidating adjustments Ally consolidated Assets Cash and cash equivalents Noninterest-bearing $ 720 $ — $ 827 $ — $ 1,547 Interest-bearing 100 — 4,287 — 4,387 Interest-bearing — intercompany — — 401 (401 ) — Total cash and cash equivalents 820 — 5,515 (401 ) 5,934 Trading securities — — 82 (82 ) — Available-for-sale securities — — 19,253 (327 ) 18,926 Held-to-maturity securities — — 839 — 839 Finance receivables and loans, net Finance receivables and loans, net 4,705 — 114,239 — 118,944 Intercompany loans to Bank subsidiary 1,125 — — (1,125 ) — Nonbank subsidiaries 1,779 — 626 (2,405 ) — Allowance for loan losses (115 ) — (1,029 ) — (1,144 ) Total finance receivables and loans, net 7,494 — 113,836 (3,530 ) 117,800 Investment in operating leases, net 42 — 11,428 — 11,470 Intercompany receivables from Bank subsidiary 299 — — (299 ) — Nonbank subsidiaries 107 — 67 (174 ) — Investment in subsidiaries Bank subsidiary 17,727 17,727 — (35,454 ) — Nonbank subsidiaries 10,318 — — (10,318 ) — Premiums receivable and other insurance assets — — 1,936 (31 ) 1,905 Other assets 4,347 — 5,085 (2,578 ) 6,854 Total assets $ 41,154 $ 17,727 $ 158,041 $ (53,194 ) $ 163,728 Liabilities Deposit liabilities Noninterest-bearing $ — $ — $ 84 $ — $ 84 Interest-bearing 167 — 78,771 — 78,938 Total deposit liabilities 167 — 78,855 — 79,022 Short-term borrowings 3,622 — 9,051 — 12,673 Long-term debt 21,798 — 32,330 — 54,128 Intercompany debt to Bank subsidiary 330 — — (330 ) — Nonbank subsidiaries 1,027 — 2,903 (3,930 ) — Intercompany payables to Nonbank subsidiaries 153 — 351 (504 ) — Interest payable 253 — 98 — 351 Unearned insurance premiums and service revenue — — 2,500 — 2,500 Accrued expenses and other liabilities 487 — 3,911 (2,661 ) 1,737 Total liabilities 27,837 — 129,999 (7,425 ) 150,411 Total equity 13,317 17,727 28,042 (45,769 ) 13,317 Total liabilities and equity $ 41,154 $ 17,727 $ 158,041 $ (53,194 ) $ 163,728 (a) Amounts presented are based upon the legal transfer of the underlying assets to VIEs in order to reflect legal ownership. Condensed Consolidating Statement of Cash Flows Nine months ended September 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Operating activities Net cash provided by operating activities $ 3,701 $ 2,900 $ 3,019 $ (6,247 ) $ 3,373 Investing activities Purchases of available-for-sale securities — — (9,022 ) — (9,022 ) Proceeds from sales of available-for-sale securities — — 2,926 — 2,926 Proceeds from maturities and repayments of available-for-sale securities — — 2,002 — 2,002 Purchases of held-to-maturity securities — — (709 ) — (709 ) Proceeds from maturities and repayments of held-to-maturity securities — — 32 — 32 Net change in investment securities — intercompany 7 — 281 (288 ) — Purchases of finance receivables and loans held-for-investment (35 ) — (3,090 ) — (3,125 ) Proceeds from sales of finance receivables and loans originated as held-for-investment 96 — 1,227 — 1,323 Originations and repayments of finance receivables and loans held-for-investment and other, net 259 — 2,718 (1,956 ) 1,021 Net change in loans — intercompany 2,159 — 232 (2,391 ) — Purchases of operating lease assets — — (2,844 ) — (2,844 ) Disposals of operating lease assets 7 — 4,402 — 4,409 Capital contributions to subsidiaries (1,200 ) — — 1,200 — Returns of contributed capital 1,031 — — (1,031 ) — Net change in restricted cash (19 ) — 521 (5 ) 497 Net change in nonmarketable equity investments — — (20 ) — (20 ) Other, net (25 ) — (43 ) (91 ) (159 ) Net cash provided by (used in) investing activities 2,280 — (1,387 ) (4,562 ) (3,669 ) Financing activities Net change in short-term borrowings — third party (245 ) — (2,255 ) — (2,500 ) Net (decrease) increase in deposits (153 ) — 12,698 (1,495 ) 11,050 Proceeds from issuance of long-term debt — third party 355 — 10,986 1,961 13,302 Repayments of long-term debt — third party (4,125 ) — (18,251 ) — (22,376 ) Net change in debt — intercompany (366 ) — (2,166 ) 2,532 — Repurchase of common stock (563 ) — — — (563 ) Dividends paid — third party (130 ) — — — (130 ) Dividends paid and returns of contributed capital — intercompany — (2,900 ) (4,459 ) 7,359 — Capital contributions from parent — — 1,200 (1,200 ) — Net cash used in financing activities (5,227 ) (2,900 ) (2,247 ) 9,157 (1,217 ) Effect of exchange-rate changes on cash and cash equivalents — — 3 — 3 Net increase (decrease) in cash and cash equivalents 754 — (612 ) (1,652 ) (1,510 ) Cash and cash equivalents at beginning of year 820 — 5,515 (401 ) 5,934 Cash and cash equivalents at September 30, $ 1,574 $ — $ 4,903 $ (2,053 ) $ 4,424 Nine months ended September 30, 2016 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Operating activities Net cash provided by operating activities $ 709 $ — $ 3,782 $ (902 ) $ 3,589 Investing activities Purchases of available-for-sale securities — — (11,027 ) — (11,027 ) Proceeds from sales of available-for-sale securities — — 8,546 — 8,546 Proceeds from maturities and repayments of available-for-sale securities — — 2,411 — 2,411 Purchases of held-to-maturity securities — — (650 ) — (650 ) Purchases of finance receivables and loans held-for-investment — — (2,924 ) — (2,924 ) Proceeds from sales of finance receivables and loans originated as held-for-investment — — 4,221 — 4,221 Originations and repayments of finance receivables and loans held-for-investment and other, net 934 — (6,318 ) — (5,384 ) Net change in loans — intercompany 1,788 — (41 ) (1,747 ) — Purchases of operating lease assets — — (2,360 ) — (2,360 ) Disposals of operating lease assets 16 — 4,615 — 4,631 Acquisitions, net of cash acquired (309 ) — — — (309 ) Capital contributions to subsidiaries (3,112 ) — — 3,112 — Returns of contributed capital 2,168 8 — (2,176 ) — Net change in restricted cash (136 ) — 758 622 Net change in nonmarketable equity investments — — (401 ) — (401 ) Other, net (156 ) — (103 ) 102 (157 ) Net cash provided by (used in) investing activities 1,193 8 (3,273 ) (709 ) (2,781 ) Financing activities Net change in short-term borrowings — third party 72 — (1,745 ) — (1,673 ) Net (decrease) increase in deposits (36 ) — 9,276 — 9,240 Proceeds from issuance of long-term debt — third party 1,084 — 10,145 — 11,229 Repayments of long-term debt — third party (2,279 ) — (18,479 ) — (20,758 ) Net change in debt — intercompany (30 ) — (1,788 ) 1,818 — Redemption of preferred stock (696 ) — — — (696 ) Repurchase of common stock (173 ) — — — (173 ) Dividends paid — third party (70 ) — — — (70 ) Dividends paid and returns of contributed capital — intercompany — (8 ) (2,968 ) 2,976 — Capital contributions from parent — — 3,112 (3,112 ) — Net cash used in financing activities (2,128 ) (8 ) (2,447 ) 1,682 (2,901 ) Effect of exchange-rate changes on cash and cash equivalents — — 2 — 2 Net decrease in cash and cash equivalents (226 ) — (1,936 ) 71 (2,091 ) Cash and cash equivalents at beginning of year 1,635 — 5,595 (850 ) 6,380 Cash and cash equivalents at September 30, $ 1,409 $ — $ 3,659 $ (779 ) $ 4,289

Contingencies and Other Risks

Contingencies and Other Risks	9 Months Ended
	Sep. 30, 2017
Loss Contingency [Abstract]
Contingencies Disclosure [Text Block]	Contingencies and Other Risks Legal Matters Ally and its subsidiaries, including Ally Bank, are or may be subject to potential liability in connection with pending or threatened legal proceedings and other matters. These legal matters may be formal or informal and include litigation and arbitration with one or more identified claimants, certified or purported class actions with yet-to-be-identified claimants, and regulatory or other governmental information-gathering requests, examinations, investigations, and enforcement proceedings. Our legal matters exist in varying stages of adjudication, arbitration, negotiation, or investigation and span our lines of business and operations. Claims may be based in law or equity—such as those arising under contracts or in tort and those involving banking, consumer-protection, securities, tax, employment, and other laws—and some can present novel legal theories and allege substantial or indeterminate damages. We accrue for a legal matter when a loss becomes probable and the amount of loss can be reasonably estimated. Accruals are evaluated each quarter and may be adjusted, upward or downward, based on our best judgment after consultation with counsel. No assurance exists that our accruals will not need to be adjusted in the future. When a probable or reasonably possible loss on a legal matter could be material to our consolidated financial condition, results of operations, or cash flows, we provide disclosure in this note as prescribed by ASC 450, Contingencies . The course and outcome of legal matters are inherently unpredictable. This is especially so when a matter is still in its early stages, the damages sought are indeterminate or unsupported, significant facts are unclear or disputed, novel questions of law or other meaningful legal uncertainties exist, a request to certify a proceeding as a class action is outstanding or granted, multiple parties are named, or regulatory or other governmental entities are involved. As a result, we often are unable to determine how or when threatened or pending legal matters will be resolved and what losses may be incurred. Actual losses may be higher or lower than any amounts accrued or estimated for those matters, possibly to a significant degree. Descriptions of our material legal matters follow. We do not believe, however, that an estimate of reasonably possible losses or a range of reasonably possible losses—whether in excess of any related accrual or where no accrual exists—can be made for any of these matters for some or all of the reasons identified in the preceding paragraph. Securities Litigation In October 2016, a purported class action—Bucks County Employees Retirement Fund v. Ally Financial Inc. et al.—was filed in the Circuit Court for Wayne County in the State of Michigan (Case No. 16-013616-CZ). This matter was removed to the U.S. District Court for the Eastern District of Michigan on November 18, 2016. The complaint alleges material misstatements and omissions in connection with Ally’s initial public offering in April 2014, including a failure to adequately disclose the severity of rising subprime automotive loan delinquency rates, deficient underwriting measures employed in the origination of subprime automotive loans, and aggressive tactics used with low-income borrowers. The request for relief includes an indeterminate amount of damages, fees, and costs and other remedies. In January 2017, another purported class action—National Shopmen Pension Fund v. Ally Financial Inc. et al.—was filed in the Circuit Court for Oakland County in the State of Michigan (Case No. 2017-156719-CB). This matter was removed to the U.S. District Court for the Eastern District of Michigan on January 30, 2017. In March 2017, a third purported class action—James McIntire v. Ally Financial Inc. et al.—was filed in the Circuit Court for Wayne County in the State of Michigan (Case No. 17-003811-CZ). This matter was removed to the U.S. District Court for the Eastern District of Michigan on March 15, 2017. The allegations and requested relief in the National Shopmen Pension Fund and James McIntire complaints are substantially similar to those included in the complaint filed by Bucks County Employees Retirement Fund. All three matters were remanded from the U.S. District Court for the Eastern District of Michigan to the state circuit courts on May 26, 2017, and have been consolidated for discovery in Wayne County Circuit Court as In re Ally Financial, Inc. Securities Litigation (Case No. 16-013616-CB). We intend to vigorously defend against each of these actions. Automotive Subprime Matters In October 2014, we received a document request from the SEC in connection with its investigation related to subprime automotive finance and related securitization activities. Separately, in December 2014, we received a subpoena from the U.S. Department of Justice requesting similar information. In May 2015 and December 2016, we received information requests from the New York Department of Financial Services requesting similar information. We have cooperated with each of these agencies with respect to these matters. Other Contingencies Ally and its subsidiaries, including Ally Bank, are or may be subject to potential liability under various other contingent exposures, including indemnification, tax, self-insurance, and other miscellaneous contingencies. We accrue for a contingent exposure when a loss becomes probable and the amount of loss can be reasonably estimated. Accruals are evaluated each quarter and may be adjusted, upward or downward, based on our best judgment. No assurance exists that our accruals will not need to be adjusted in the future, and actual losses may be higher or lower than any amounts accrued or estimated for those exposures, possibly to a significant degree. On the basis of information currently available, we do not believe that these other contingent exposures will be material to our consolidated financial condition, results of operations, or cash flows. Refer to Note 1 to the Consolidated Financial Statements included in our 2016 Annual Report on Form 10-K for additional information related to our policy for establishing reserves for legal and regulatory matters.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events Declaration of Quarterly Dividend Payment On October 10, 2017 , the Ally Board of Directors declared a quarterly cash dividend payment of $0.12 per share on all common stock. The dividend is payable on November 15, 2017 , to shareholders of record at the close of business on November 1, 2017.

Description of Business, Basi33

Description of Business, Basis of Presentation, and Changes in Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting, Policy [Policy Text Block]	Our accounting and reporting policies conform to accounting principles generally accepted in the United States of America (GAAP). Additionally, where applicable, the policies conform to the accounting and reporting guidelines prescribed by bank regulatory authorities.
Use of Estimates, Policy [Policy Text Block]	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and that affect income and expenses during the reporting period and related disclosures. In developing the estimates and assumptions, management uses all available evidence; however, actual results could differ because of uncertainties associated with estimating the amounts, timing, and likelihood of possible outcomes. Our most significant estimates pertain to the allowance for loan losses, valuations of automotive lease assets and residuals, fair value of financial instruments, legal and regulatory reserves, and the determination of the provision for income taxes.
Income Tax, Policy [Policy Text Block]	Income Taxes In calculating the provision for interim income taxes, in accordance with Accounting Standards Codification (ASC) 740, Income Taxes , we apply an estimated annual effective tax rate to year-to-date ordinary income. At the end of each interim period, we estimate the effective tax rate expected to be applicable for the full fiscal year. This method differs from that described in Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K, which describes our annual significant income tax accounting policy and related methodology.
Transfers and Servicing of Financial Assets, Transfers of Financial Assets, Policy [Policy Text Block]	Securitizations and Variable Interest Entities We securitize, transfer, and service consumer and commercial automotive loans and operating leases. Securitization transactions typically involve the use of variable interest entities (VIEs) and are accounted for either as sales or secured borrowings. We may retain economic interests in securitized and sold assets, which are generally in the form of senior or subordinated interests, other residual interests, and servicing rights. In order to conclude whether or not a VIE is required to be consolidated, careful consideration and judgment must be given to our continuing involvement with the VIE. In circumstances where we have both the power to direct the activities of the entity that most significantly impact the entity's performance and the obligation to absorb losses or the right to receive benefits of the entity that could be significant, we would conclude that we are the primary beneficiary of the VIE, and would consolidate the entity. Consolidation of the VIE would also preclude us from recording an accounting sale on the transaction. In the case of a consolidated VIE, the accounting is consistent with a secured borrowing (e.g., we continue to carry the loans and we record the related securitized debt on our Condensed Consolidated Balance Sheet ). In transactions where we are not determined to be the primary beneficiary of the VIE, we must determine whether or not we achieve a sale for accounting purposes. In order to achieve a sale for accounting purposes, the assets being transferred must be legally isolated, not be constrained by restrictions from further transfer, and be deemed to be beyond our control. If we were to fail any of these three criteria for sale accounting, the transfer would be accounted for as a secured borrowing consistent with the preceding paragraph . Refer to Note 10 to the Condensed Consolidated Financial Statements for discussion on VIEs. Gains or losses on off-balance sheet securitizations take into consideration the fair value of any retained interests, including the value of certain servicing assets or liabilities, if any, which are initially recorded at fair value at the date of sale. The estimate of the fair value of the retained interests and servicing requires us to exercise significant judgment about the timing and amount of future cash flows from the interests. Refer to Note 21 to the Condensed Consolidated Financial Statements for a discussion of fair value estimates. Gains or losses on off-balance sheet securitizations and sales are reported in gain on mortgage and automotive loans, net, in our Condensed Consolidated Statement of Comprehensive Income . Retained interests are classified as securities or as other assets depending on their nature. On December 24, 2016, the risk retention rules under the Dodd-Frank Wall Street Reform and Consumer Protection Act (Dodd-Frank Act) of 2010 became effective, requiring us to retain at least five percent of the credit risk of the assets underlying asset-backed securitizations . This note was updated to address the Dodd-Frank Act risk retention rules and differs from our description in Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K. We retain servicing responsibilities for all of our consumer and commercial automotive loan and operating lease securitizations. We may receive servicing fees for off-balance sheet securitizations based on the securitized loan balances and certain ancillary fees, all of which are reported in servicing fees in the Condensed Consolidated Statement of Comprehensive Income. Typically, the fee we are paid for servicing consumer automotive finance receivables represents adequate compensation, and consequently, does not result in the recognition of a servicing asset or liability. Whether on- or off-balance sheet, the investors in the securitization trusts generally have no recourse to our assets outside of protections afforded through customary market representation and warranty repurchase provisions. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K regarding additional significant accounting policies.
New Accounting Pronouncements, Policy [Text Block]	Recently Adopted Accounting Standards Stock Compensation — Improvements to Employee Share-Based Payment Accounting (ASU 2016-09) As of December 31, 2016, we adopted Accounting Standards Update (ASU) 2016-09. The amendments in this update changed several aspects of share-based payment accounting. The amendments allowed for an entity-wide accounting policy election to either account for forfeitures as they occur or estimate the number of awards that are expected to vest. We elected to account for forfeitures as they occur. The amendments modified the tax withholding requirements to allow entities to withhold an amount up to the employee’s maximum individual statutory tax rates without resulting in a liability classification of the award as opposed to limiting the withholding to the minimum statutory tax rates as required under previous accounting guidance. The amendments required that all excess tax benefits and tax deficiencies related to share-based payment awards be recognized in income tax expense or benefit in the income statement in the period in which they occur. The amendments also addressed the classification and presentation of certain items on the cash flow statement. Specifically, cash flows related to excess tax benefits should be classified as an operating activity instead of a financing activity and cash flows related to cash paid to a tax authority by an employer when withholding shares from an employee’s award for tax withholding purposes should be classified as a financing activity. The adoption of these amendments did not have a material impact to the financial statements. Recently Issued Accounting Standards Revenue from Contracts with Customers (ASU 2014-09) and Revenue from Contracts with Customers — Deferral of the Effective Date (ASU 2015-14) In May 2014, the Financial Accounting Standards Board (FASB) issued ASU 2014-09. The purpose of this guidance is to streamline and consolidate existing revenue recognition principles in GAAP and to converge revenue recognition principles with International Financial Reporting Standards (IFRS). The core principle of the amendments is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to receive in exchange for those goods or services. The amendments include a five step process for consideration of the core principle, guidance on the accounting treatment for costs associated with a contract, and disclosure requirements related to the revenue process. As originally issued, the amendments in ASU 2014-09 were to be effective beginning on January 1, 2017. However, in August 2015, the FASB issued ASU 2015-14, which deferred the effective date of the guidance until January 1, 2018, and permitted early adoption as of the original effective date in ASU 2014-09. The FASB has issued several additional ASUs to clarify guidance and provide implementation support for ASU 2014-09. Management has considered these additional ASUs when assessing the overall impact of ASU 2014-09. The amendments to the revenue recognition principles can be applied upon adoption either through a full retrospective application or on a modified retrospective basis with a cumulative effect adjustment on the date of initial adoption with certain practical expedients. Our implementation efforts to date related to this standard have included identifying revenue streams that are within the scope of this guidance, the evaluation of associated contracts and accounting policies, the evaluation of processes and systems of internal control, and the assessment of disclosure requirements of the standard. A majority of our revenue streams are not within the scope of this ASU as they are governed by other accounting standards. Management has determined that certain revenue streams and contractual arrangements are in scope of this guidance, including deposit fees, revenue on certain noninsurance contracts, brokering commissions through our insurance operations, sales of off-lease vehicles, remarketing fee income through SmartAuction, and commission and fee income generated through Ally Invest. Management does not expect these amendments to impact current revenue recognition patterns for a majority of the in scope revenue streams and contracts. However, we expect that the application of this guidance to noninsurance contracts within our insurance business will result in the deferral of certain amounts we currently recognize as revenue and expense upon the origination of the contract and the immediate recognition of certain expenses upon the origination of the contract that are currently deferred. Additionally, upon implementation we expect to expand our financial statement disclosures as required by the standard. Our assessment is not final; however, we do not expect the impact of the new guidance to these specific contracts to be material to the financial statements. We currently plan to adopt this guidance as of January 1, 2018, and expect to use the modified retrospective approach. Financial Instruments — Recognition and Measurement of Financial Assets (ASU 2016-01) In January 2016, the FASB issued ASU 2016-01. The amendments in this update modify the requirements related to the measurement of certain financial instruments in the statement of financial condition and results of operations. For equity investments (other than investments accounted for using the equity method), entities must measure such instruments at fair value with changes in fair value recognized in net income. Changes in fair value for equity securities will no longer be recognized through other comprehensive income. Reporting entities may continue to elect to measure equity investments that do not have a readily determinable fair value at cost with adjustments for impairment and observable changes in price. In addition, for a liability (other than a derivative liability) that an entity measures at fair value, any change in fair value related to the instrument-specific credit risk, that is the entity’s own-credit, should be presented separately in other comprehensive income and not as a component of net income. The amendments are effective on January 1, 2018, with early adoption permitted solely for the provisions pertaining to instrument-specific credit risk for liabilities measured at fair value. The amendments must be applied on a modified retrospective basis with a cumulative effect adjustment as of the beginning of the fiscal year of initial adoption. While the amendment requiring equity investments to be measured at fair value with changes in fair value recognized in net income will create additional volatility in our Condensed Consolidated Statement of Comprehensive Income , we do not anticipate the other amendments will have a material impact to our financial statements. We currently plan to adopt these amendments on January 1, 2018, and expect to use the modified retrospective approach as required. Leases (ASU 2016-02) In February 2016, the FASB issued ASU 2016-02. The amendments in this update primarily replace the existing accounting requirements for operating leases for lessees. Lessee accounting requirements for finance leases and lessor accounting requirements for operating leases and sales type and direct financing leases (sales type and direct financing leases were both previously referred to as capital leases) are largely unchanged. The amendments require the lessee of an operating lease to record a balance sheet gross-up upon lease commencement by recognizing a right-of-use asset and lease liability equal to the present value of the lease payments. The right-of-use asset and lease liability should be derecognized in a manner that effectively yields a straight line lease expense over the lease term. In addition to the changes to the lessee operating lease accounting requirements, the amendments also change the types of costs that can be capitalized related to a lease agreement for both lessees and lessors for all types of leases. The amendments also require additional disclosures for all lease types for both lessees and lessors. The amendments are effective on January 1, 2019, with early adoption permitted. The amendments must be applied on a modified retrospective basis with a cumulative adjustment to the beginning of the earliest fiscal year presented in the financial statements in the period of adoption. Management is currently evaluating the impact of these amendments. Upon adoption, we expect to record a balance sheet gross-up, reflecting our right-of-use asset and lease liability for our operating leases where we are the lessee (for example, our facility leases). We are currently reviewing our operating lease contracts where we are the lessee to determine the impact of the gross-up and the changes to capitalizable costs. We are also reviewing our leases where we are the lessor to determine the impact of the changes to capitalizable costs. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as required. Financial Instruments — Credit Losses (ASU 2016-13) In June 2016, the FASB issued ASU 2016-13. The amendments in this update introduce a new accounting model to measure credit losses for financial assets measured at amortized cost. Credit losses for financial assets measured at amortized cost should be determined based on the total current expected credit losses over the life of the financial asset or group of financial assets. In effect, the financial asset or group of financial assets should be presented at the net amount expected to be collected. Credit losses will no longer be measured as they are incurred for financial assets measured at amortized cost. The amendments also modify the accounting for available-for-sale debt securities whereby credit losses will be recorded through an allowance for credit losses rather than a write-down to the security’s cost basis, which allows for reversals of credit losses when estimated credit losses decline. Credit losses for available-for-sale debt securities should be measured in a manner similar to current GAAP. The amendments are effective on January 1, 2020, with early adoption permitted as of January 1, 2019. The amendments must be applied using a modified retrospective approach with a cumulative-effect adjustment through retained earnings as of the beginning of the fiscal year upon adoption. The new accounting model for credit losses represents a significant departure from existing GAAP, and will likely materially increase the allowance for credit losses with a resulting negative adjustment to retained earnings. Management created a formal working group to govern the implementation of these amendments consisting of key stakeholders from finance, risk, and accounting and is currently evaluating the impact of the amendments. We are in the process of designing and building the models and procedures that will be used to calculate the credit loss reserves in accordance with these amendments. We currently plan to adopt these amendments on January 1, 2020, and expect to use the modified retrospective approach as required. Statement of Cash Flows — Restricted Cash (ASU 2016-18) In November 2016, the FASB issued ASU 2016-18. The amendments in this update require that amounts classified as restricted cash and restricted cash equivalents be included within the beginning-of-period and end-of-period amounts along with cash and cash equivalents on the statement of cash flows. Prior to this ASU, specific guidance on the presentation of changes in restricted cash and restricted cash equivalents within the statement of cash flows did not exist. The amendments are effective on January 1, 2018, with early adoption permitted. The amendments must be applied retrospectively to all periods presented within the statement of cash flows upon adoption. The amendments will not impact financial results, but will result in a change in the presentation of restricted cash and restricted cash equivalents within the statement of cash flows. We currently plan to adopt these amendments on January 1, 2018, and expect to use the retrospective approach as required. Receivables — Nonrefundable Fees and Other Costs: Premium Amortization on Purchased Callable Debt Securities (ASU 2017-08) In March 2017, the FASB issued ASU 2017-08. The amendments in this update require premiums on purchased callable debt securities to be amortized to the security’s earliest call date. Prior to this ASU, premiums and discounts on purchased callable debt securities were generally required to be amortized to the security’s maturity date. The amendments do not require an accounting change for securities held at a discount. The amendments are effective on January 1, 2019, with early adoption permitted. The amendments must be applied using a modified retrospective approach with a cumulative-effect adjustment through retained earnings as of the beginning of the fiscal year upon adoption. Management is currently evaluating the impact of these amendments. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as required. Derivatives and Hedging — Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12) In August 2017, the FASB issued ASU 2017-12, which enhances the financial reporting of hedging relationships to better portray the economic results of an entity's risk management activities in its financial statements and make certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP. The amendments in this update better align an entity's risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and presentation of hedge results. The amendments are effective on January 1, 2019, with early adoption permitted. Entities must apply the amendments to cash flow and net investment hedge relationships that exist on the date of adoption using a modified retrospective approach. All transition requirements and elections must be applied to hedging relationships existing as of the adoption date and the effect of adoption should be reflected as of the beginning of the fiscal year of adoption. The presentation and disclosure requirements must be applied prospectively. We are currently evaluating the impact these amendments will have to our financial statements and are evaluating the potential of early adopting the standard on January 1, 2018.

Discontinued Operations Discont

Discontinued Operations Discontinued Operations (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Discontinued Operations, Policy [Policy Text Block]	Prior to the adoption of ASU 2014-08, which was prospectively applied only to newly identified disposals that qualify as discontinued operations beginning after January 1, 2015, we have classified operations as discontinued when operations and cash flows will be eliminated from our ongoing operations and we do not expect to retain any significant continuing involvement in their operations after the respective sale or disposal transactions. For all periods presented, the operating results for these discontinued operations have been removed from continuing operations and presented separately as discontinued operations, net of tax, in the Condensed Consolidated Statement of Comprehensive Income . The Notes to the Condensed Consolidated Financial Statements have been adjusted to exclude discontinued operations unless otherwise noted.

Acquisitions Acquisitions (Tabl

Acquisitions Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2017
Acquisitions [Abstract]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	The following table summarizes the allocation of cash consideration paid for TradeKing and the amounts of the identifiable assets acquired and liabilities assumed recognized at the acquisition date. ($ in millions) Purchase price Cash consideration $ 298 Allocation of purchase price to net assets acquired Intangible assets (a) 82 Cash and short-term investments (b) 50 Other assets 14 Deferred tax asset, net 4 Employee compensation and benefits (41 ) Other liabilities (4 ) Goodwill $ 193 (a) We recorded $3 million and $8 million of amortization on these intangible assets during the three months and nine months ended September 30, 2017 , respectively, and $3 million during both the three months and nine months ended September 30, 2016 . (b) Includes $40 million in cash proceeds from the acquisition transaction in order to pay employee compensation and benefits that vested upon acquisition as a result of the change in control.

Discontinued Operations (Tables

Discontinued Operations (Tables)	9 Months Ended
	Sep. 30, 2017
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations [Table Text Block]	Select financial information of discontinued operations is summarized below. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Pretax loss $ (1 ) $ (46 ) $ (2 ) $ (44 ) Tax (benefit) expense (3 ) 6 (3 ) 2

Other Income, Net of Losses (Ta

Other Income, Net of Losses (Tables)	9 Months Ended
	Sep. 30, 2017
Other Nonoperating Income (Expense) [Abstract]
Schedule of Other Nonoperating Income, by Component [Table Text Block]	Details of other income, net of losses, were as follows. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Remarketing fees $ 26 $ 26 $ 82 $ 79 Late charges and other administrative fees 25 25 77 72 Servicing fees 11 18 41 49 Income from equity-method investments 7 3 12 14 Other, net 26 26 101 75 Total other income, net of losses $ 95 $ 98 $ 313 $ 289

Reserves for Insurance Losses38

Reserves for Insurance Losses and Loss Adjustment Expenses Reserves for Insurance Losses and Loss Adjustment Expenses (Tables)	9 Months Ended
	Sep. 30, 2017
Reserves for Insurance Losses and Loss Adjustment Expenses [Abstract]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense	The following table shows a rollforward of our reserves for insurance losses and loss adjustment expenses. ($ in millions) 2017 2016 Total gross reserves for insurance losses and loss adjustment expenses at January 1, $ 149 $ 169 Less: Reinsurance recoverable 108 120 Net reserves for insurance losses and loss adjustment expenses at January 1, 41 49 Net insurance losses and loss adjustment expenses incurred related to: Current year 276 291 Prior years (a) 2 (4 ) Total net insurance losses and loss adjustment expenses incurred 278 287 Net insurance losses and loss adjustment expenses paid or payable related to: Current year (248 ) (266 ) Prior years (31 ) (27 ) Total net insurance losses and loss adjustment expenses paid or payable (279 ) (293 ) Foreign exchange and other 1 1 Net reserves for insurance losses and loss adjustment expenses at September 30, 41 44 Plus: Reinsurance recoverable 132 106 Total gross reserves for insurance losses and loss adjustment expenses at September 30, $ 173 $ 150 (a) There have been no material adverse changes to the reserve for prior years.

Other Operating Expenses (Table

Other Operating Expenses (Tables)	9 Months Ended
	Sep. 30, 2017
Operating Expenses [Abstract]
Schedule of Other Operating Cost and Expense, by Component [Table Text Block]	Details of other operating expenses were as follows. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Insurance commissions $ 106 $ 99 $ 309 $ 290 Technology and communications 72 70 212 203 Lease and loan administration 41 34 116 100 Advertising and marketing 33 27 96 75 Vehicle remarketing and repossession 29 24 82 70 Regulatory and licensing fees 27 26 82 68 Professional services 28 25 81 75 Premises and equipment depreciation 22 19 67 61 Occupancy 11 13 34 38 Non-income taxes 6 10 22 27 Other 49 71 148 182 Total other operating expenses $ 424 $ 418 $ 1,249 $ 1,189

Investment Securities (Tables)

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Investment [Table Text Block]	Our portfolio of securities includes bonds, equity securities, asset-backed securities, commercial and residential mortgage-backed securities, and other investments. The cost, fair value, and gross unrealized gains and losses on investment securities were as follows. September 30, 2017 December 31, 2016 Amortized cost Gross unrealized Fair value Amortized cost Gross unrealized Fair ($ in millions) gains losses gains losses Available-for-sale securities Debt securities U.S. Treasury (a) $ 2,112 $ — $ (39 ) $ 2,073 $ 1,680 $ — $ (60 ) $ 1,620 U.S. States and political subdivisions 849 12 (10 ) 851 794 7 (19 ) 782 Foreign government 157 2 (2 ) 157 157 5 — 162 Agency mortgage-backed residential 14,423 54 (133 ) 14,344 10,473 29 (212 ) 10,290 Mortgage-backed residential 2,326 16 (32 ) 2,310 2,162 5 (70 ) 2,097 Mortgage-backed commercial 509 2 (2 ) 509 537 2 (2 ) 537 Asset-backed 1,036 4 (1 ) 1,039 1,396 6 (2 ) 1,400 Corporate debt 1,291 10 (10 ) 1,291 1,452 7 (16 ) 1,443 Total debt securities (b) (c) 22,703 100 (229 ) 22,574 18,651 61 (381 ) 18,331 Equity securities 563 12 (50 ) 525 642 7 (54 ) 595 Total available-for-sale securities $ 23,266 $ 112 $ (279 ) $ 23,099 $ 19,293 $ 68 $ (435 ) $ 18,926 Held-to-maturity securities Debt securities Agency mortgage-backed residential (d) $ 1,799 $ 4 $ (36 ) $ 1,767 $ 839 $ — $ (50 ) $ 789 Asset-backed retained notes 40 — — 40 — — — — Total held-to-maturity securities $ 1,839 $ 4 $ (36 ) $ 1,807 $ 839 $ — $ (50 ) $ 789 (a) Includes $304 million of U.S. Treasury securities that are included in a fair value hedging relationship as of September 30, 2017. Refer to Note 19 for additional information. (b) Certain entities related to our Insurance operations are required to deposit securities with state regulatory authorities. These deposited securities totaled $12 million and $14 million at September 30, 2017 , and December 31, 2016 , respectively. (c) Investment securities with a fair value of $6,705 million and $4,881 million at September 30, 2017 , and December 31, 2016 , respectively, were pledged to secure advances from the Federal Home Loan Bank (FHLB), short-term borrowings or repurchase agreements, or for other purposes as required by contractual obligation or law. Under these agreements, we have granted the counterparty the right to sell or pledge $1,339 million and $737 million of the underlying investment securities at September 30, 2017 , and December 31, 2016 , respectively. (d) Agency mortgage-backed residential debt securities are held for liquidity risk management purposes. Securities with a fair value of $115 million and $87 million at September 30, 2017 , and December 31, 2016 , respectively, were pledged to secure advances from the FHLB.
Investments Classified by Contractual Maturity Date [Table Text Block]	The maturity distribution of investment securities outstanding is summarized in the following tables. Call or prepayment options may cause actual maturities to differ from contractual maturities. Total Due in one year or less Due after one year through five years Due after five years through ten years Due after ten years ($ in millions) Amount Yield Amount Yield Amount Yield Amount Yield Amount Yield September 30, 2017 Fair value of available-for-sale debt securities (a) U.S. Treasury $ 2,073 1.8 % $ — — % $ 467 1.7 % $ 1,606 1.8 % $ — — % U.S. States and political subdivisions 851 2.9 69 1.6 35 2.4 197 2.7 550 3.2 Foreign government 157 2.5 — — 69 2.6 88 2.4 — — Agency mortgage-backed residential 14,344 3.1 — — — — 3 2.9 14,341 3.1 Mortgage-backed residential 2,310 3.0 — — — — — — 2,310 3.0 Mortgage-backed commercial 509 3.1 — — — — 31 2.9 478 3.1 Asset-backed 1,039 3.0 2 1.6 762 3.1 137 3.1 138 2.7 Corporate debt 1,291 2.9 135 2.5 595 2.6 515 3.2 46 4.9 Total available-for-sale debt securities $ 22,574 2.9 $ 206 2.2 $ 1,928 2.6 $ 2,577 2.2 $ 17,863 3.1 Amortized cost of available-for-sale debt securities $ 22,703 $ 206 $ 1,929 $ 2,609 $ 17,959 Amortized cost of held-to-maturity securities Agency mortgage-backed residential $ 1,799 3.1 % $ — — % $ — — % $ — — % $ 1,799 3.1 % Asset-backed retained notes 40 1.7 — — 39 1.6 1 3.0 — — Total held-to-maturity securities $ 1,839 3.1 $ — — $ 39 1.6 $ 1 3.0 $ 1,799 3.1 December 31, 2016 Fair value of available-for-sale debt securities (a) U.S. Treasury $ 1,620 1.7 % $ 2 4.6 % $ 60 1.6 % $ 1,558 1.7 % $ — — % U.S. States and political subdivisions 782 3.1 64 1.7 29 2.3 172 2.8 517 3.4 Foreign government 162 2.6 — — 58 2.8 104 2.4 — — Agency mortgage-backed residential 10,290 2.9 — — — — 29 2.6 10,261 2.9 Mortgage-backed residential 2,097 2.9 — — — — — — 2,097 2.9 Mortgage-backed commercial 537 2.6 — — — — 3 2.8 534 2.6 Asset-backed 1,400 2.8 — — 1,059 2.8 143 3.2 198 2.6 Corporate debt 1,443 2.8 72 2.2 840 2.6 489 3.2 42 4.7 Total available-for-sale debt securities $ 18,331 2.8 $ 138 2.0 $ 2,046 2.7 $ 2,498 2.2 $ 13,649 2.9 Amortized cost of available-for-sale debt securities $ 18,651 $ 138 $ 2,040 $ 2,563 $ 13,910 Amortized cost of held-to-maturity securities (b) $ 839 2.9 % $ — — % $ — — % $ — — % $ 839 2.9 % (a) Yield is calculated using the effective yield of each security at the end of the period, weighted based on the market value. The effective yield considers the contractual coupon and amortized cost, and excludes expected capital gains and losses. (b) Our held-to-maturity securities portfolio as of December 31, 2016, consisted of agency mortgage-backed residential debt securities.
Investment Income [Table Text Block]	The following table presents interest and dividends on investment securities. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Taxable interest $ 141 $ 93 $ 390 $ 276 Taxable dividends 3 4 8 13 Interest and dividends exempt from U.S. federal income tax 6 4 17 13 Interest and dividends on investment securities $ 150 $ 101 $ 415 $ 302
Schedule of Realized Gain (Loss) [Table Text Block]	The following table presents gross gains and losses realized upon the sales of available-for-sale securities. There were no other-than-temporary impairments upon the sales of available-for-sale securities for either period. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Gross realized gains $ 24 $ 52 $ 75 $ 146 Gross realized losses (a) (1 ) — (2 ) (1 ) Other gain on investments, net $ 23 $ 52 $ 73 $ 145 (a) Certain available-for-sale securities were sold at a loss in 2017 and 2016 as a result of market conditions within these respective periods (e.g., a downgrade in the rating of a debt security). Any such sales were made in accordance with our risk management policies and practices.
Schedule of Unrealized Loss on Investments [Table Text Block]	The table below summarizes available-for-sale securities in an unrealized loss position in accumulated other comprehensive income. Based on the assessment of whether such losses were deemed to be other-than-temporary, we believe that the unrealized losses are not indicative of an other-than-temporary impairment of these securities. As of September 30, 2017 , we did not have the intent to sell the debt securities with an unrealized loss position in accumulated other comprehensive income, it is not more likely than not that we will be required to sell these securities before recovery of their amortized cost basis, and we expect to recover the entire amortized cost basis of the securities. As of September 30, 2017 , we had the ability and intent to hold equity securities with an unrealized loss position in accumulated other comprehensive income, and it is not more likely than not that we will be required to sell these securities before recovery of their amortized cost basis. As a result, we believe that the securities with an unrealized loss position in accumulated other comprehensive income are not considered to be other-than-temporarily impaired at September 30, 2017 . Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for additional information related to investment securities and our methodology for evaluating potential other-than-temporary impairments. September 30, 2017 December 31, 2016 Less than 12 months 12 months or longer Less than 12 months 12 months or longer ($ in millions) Fair value Unrealized loss Fair value Unrealized loss Fair value Unrealized loss Fair value Unrealized loss Available-for-sale securities Debt securities U.S. Treasury $ 2,029 $ (39 ) $ — $ — $ 1,612 $ (60 ) $ — $ — U.S. States and political subdivisions 311 (4 ) 138 (6 ) 524 (19 ) — — Foreign government 78 (2 ) — — 38 — — — Agency mortgage-backed residential 7,444 (115 ) 730 (18 ) 8,052 (196 ) 587 (16 ) Mortgage-backed residential 103 (1 ) 825 (31 ) 813 (17 ) 860 (53 ) Mortgage-backed commercial 164 (2 ) 15 — 47 (1 ) 149 (1 ) Asset-backed 341 (1 ) 86 — 375 (2 ) 127 — Corporate debt 388 (6 ) 108 (4 ) 744 (14 ) 46 (2 ) Total temporarily impaired debt securities 10,858 (170 ) 1,902 (59 ) 12,205 (309 ) 1,769 (72 ) Temporarily impaired equity securities 101 (8 ) 119 (42 ) 151 (8 ) 269 (46 ) Total temporarily impaired available-for-sale securities $ 10,959 $ (178 ) $ 2,021 $ (101 ) $ 12,356 $ (317 ) $ 2,038 $ (118 )

Finance Receivables and Loans41

Finance Receivables and Loans, Net (Tables)	9 Months Ended
	Sep. 30, 2017
Loans and Leases Receivable, Net Amount [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]	The composition of finance receivables and loans reported at gross carrying value was as follows. ($ in millions) September 30, 2017 December 31, 2016 Consumer automotive (a) $ 67,077 $ 65,793 Consumer mortgage Mortgage Finance (b) 9,760 8,294 Mortgage — Legacy (c) 2,255 2,756 Total consumer mortgage 12,015 11,050 Total consumer 79,092 76,843 Commercial Commercial and industrial Automotive 31,985 35,041 Other 3,774 3,248 Commercial real estate — Automotive 4,020 3,812 Total commercial 39,779 42,101 Total finance receivables and loans (d) $ 118,871 $ 118,944 (a) Includes $24 million and $43 million of fair value adjustment for loans in hedge accounting relationships at September 30, 2017 , and December 31, 2016 , respectively. Refer to Note 19 for additional information. (b) Includes loans originated as interest-only mortgage loans of $24 million and $30 million at September 30, 2017 , and December 31, 2016 , respectively, 35% of which are expected to start principal amortization in 2019 , and 44% in 2020 . The remainder of these loans have already exited the interest-only period. (c) Includes loans originated as interest-only mortgage loans of $538 million and $714 million at September 30, 2017 , and December 31, 2016 , respectively, 2% of which are expected to start principal amortization in 2018 , and 1% beyond 2020. The remainder of these loans have already exited the interest-only period. (d) Totals include net increases of $494 million and $359 million at September 30, 2017 , and December 31, 2016 , respectively, for unearned income, unamortized premiums and discounts, and deferred fees and costs.
Allowance for Credit Losses on Financing Receivables [Table Text Block]	The following tables present an analysis of the activity in the allowance for loan losses on finance receivables and loans. Three months ended September 30, 2017 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at July 1, 2017 $ 1,002 $ 83 $ 140 $ 1,225 Charge-offs (a) (327 ) (7 ) (10 ) (344 ) Recoveries 85 6 — 91 Net charge-offs (242 ) (1 ) (10 ) (253 ) Provision for loan losses 314 — — 314 Other — (1 ) 1 — Allowance at September 30, 2017 $ 1,074 $ 81 $ 131 $ 1,286 (a) Represents the amount of the gross carrying value directly written off. For consumer and commercial loans, the loss from a charge-off is measured as the difference between the gross carrying value of a loan and the fair value of the collateral, less costs to sell. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for more information regarding our charge-off policies. Three months ended September 30, 2016 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at July 1, 2016 $ 862 $ 109 $ 118 $ 1,089 Charge-offs (a) (293 ) (10 ) — (303 ) Recoveries 74 16 — 90 Net charge-offs (219 ) 6 — (213 ) Provision for loan losses 269 (15 ) 4 258 Allowance at September 30, 2016 $ 912 $ 100 $ 122 $ 1,134 (a) Represents the amount of the gross carrying value directly written off. For consumer and commercial loans, the loss from a charge-off is measured as the difference between the gross carrying value of a loan and the fair value of the collateral, less costs to sell. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for more information regarding our charge-off policies. Nine months ended September 30, 2017 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at January 1, 2017 $ 932 $ 91 $ 121 $ 1,144 Charge-offs (a) (958 ) (22 ) (10 ) (990 ) Recoveries 266 19 — 285 Net charge-offs (692 ) (3 ) (10 ) (705 ) Provision for loan losses 841 (6 ) 19 854 Other (b) (7 ) (1 ) 1 (7 ) Allowance at September 30, 2017 $ 1,074 $ 81 $ 131 $ 1,286 Allowance for loan losses at September 30, 2017 Individually evaluated for impairment $ 35 $ 30 $ 21 $ 86 Collectively evaluated for impairment 1,039 51 110 1,200 Finance receivables and loans at gross carrying value Ending balance $ 67,077 $ 12,015 $ 39,779 $ 118,871 Individually evaluated for impairment 403 237 146 786 Collectively evaluated for impairment 66,674 11,778 39,633 118,085 (a) Represents the amount of the gross carrying value directly written off. For consumer and commercial loans, the loss from a charge-off is measured as the difference between the gross carrying value of a loan and the fair value of the collateral, less costs to sell. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for more information regarding our charge-off policies. (b) Primarily related to the transfer of finance receivables and loans from held-for-investment to held-for-sale. Nine months ended September 30, 2016 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at January 1, 2016 $ 834 $ 114 $ 106 $ 1,054 Charge-offs (a) (773 ) (29 ) (1 ) (803 ) Recoveries 233 25 1 259 Net charge-offs (540 ) (4 ) — (544 ) Provision for loan losses 644 (10 ) 16 650 Other (b) (26 ) — — (26 ) Allowance at September 30, 2016 $ 912 $ 100 $ 122 $ 1,134 Allowance for loan losses at September 30, 2016 Individually evaluated for impairment $ 24 $ 35 $ 25 $ 84 Collectively evaluated for impairment 888 65 97 1,050 Finance receivables and loans at gross carrying value Ending balance $ 64,816 $ 10,857 $ 39,286 $ 114,959 Individually evaluated for impairment 349 251 111 711 Collectively evaluated for impairment 64,467 10,606 39,175 114,248 (a) Represents the amount of the gross carrying value directly written off. For consumer and commercial loans, the loss from a charge-off is measured as the difference between the gross carrying value of a loan and the fair value of the collateral, less costs to sell. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for more information regarding our charge-off policies. (b) Primarily related to the transfer of finance receivables and loans from held-for-investment to held-for-sale.
Schedule Of Sales Of Financing Receivables And Loans [Table Text Block]	The following table presents information about significant sales of finance receivables and loans and transfers of finance receivables and loans from held-for-investment to held-for-sale. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Consumer automotive $ 28 $ 57 $ 1,326 $ 4,216 Consumer mortgage 3 6 9 12 Commercial — — — 28 Total sales and transfers $ 31 $ 63 $ 1,335 $ 4,256
Schedule of Purchases of Financing Receivables and Loans [Table Text Block]	The following table presents information about significant purchases of finance receivables and loans. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Consumer automotive $ 83 $ — $ 762 $ — Consumer mortgage 1,183 467 2,319 2,855 Total purchases of finance receivables and loans $ 1,266 $ 467 $ 3,081 $ 2,855
Past Due Financing Receivables [Table Text Block]	The following table presents an analysis of our past due finance receivables and loans recorded at gross carrying value. ($ in millions) 30–59 days past due 60–89 days past due 90 days or more past due Total past due Current Total finance receivables and loans September 30, 2017 Consumer automotive $ 1,742 $ 414 $ 261 $ 2,417 $ 64,660 $ 67,077 Consumer mortgage Mortgage Finance 75 1 5 81 9,679 9,760 Mortgage — Legacy 40 21 58 119 2,136 2,255 Total consumer mortgage 115 22 63 200 11,815 12,015 Total consumer 1,857 436 324 2,617 76,475 79,092 Commercial Commercial and industrial Automotive 16 — 13 29 31,956 31,985 Other — — 8 8 3,766 3,774 Commercial real estate — Automotive 3 — — 3 4,017 4,020 Total commercial 19 — 21 40 39,739 39,779 Total consumer and commercial $ 1,876 $ 436 $ 345 $ 2,657 $ 116,214 $ 118,871 December 31, 2016 Consumer automotive $ 1,850 $ 428 $ 302 $ 2,580 $ 63,213 $ 65,793 Consumer mortgage Mortgage Finance 39 6 4 49 8,245 8,294 Mortgage — Legacy 45 18 57 120 2,636 2,756 Total consumer mortgage 84 24 61 169 10,881 11,050 Total consumer 1,934 452 363 2,749 74,094 76,843 Commercial Commercial and industrial Automotive 3 — 7 10 35,031 35,041 Other — — — — 3,248 3,248 Commercial real estate — Automotive — — — — 3,812 3,812 Total commercial 3 — 7 10 42,091 42,101 Total consumer and commercial $ 1,937 $ 452 $ 370 $ 2,759 $ 116,185 $ 118,944
Schedule of Financing Receivables, Non Accrual Status [Table Text Block]	The following table presents the gross carrying value of our finance receivables and loans on nonaccrual status. ($ in millions) September 30, 2017 December 31, 2016 Consumer automotive $ 573 $ 598 Consumer mortgage Mortgage Finance 7 10 Mortgage — Legacy 81 89 Total consumer mortgage 88 99 Total consumer 661 697 Commercial Commercial and industrial Automotive 78 33 Other 61 84 Commercial real estate — Automotive 7 5 Total commercial 146 122 Total consumer and commercial finance receivables and loans $ 807 $ 819
Financing Receivable Credit Quality Indicators [Table Text Block]	The following table presents performing and nonperforming credit quality indicators in accordance with our internal accounting policies for our consumer finance receivables and loans recorded at gross carrying value. Nonperforming loans include finance receivables and loans on nonaccrual status when the principal or interest has been delinquent for 90 days or when full collection is not expected. Refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for additional information. September 30, 2017 December 31, 2016 ($ in millions) Performing Nonperforming Total Performing Nonperforming Total Consumer automotive $ 66,504 $ 573 $ 67,077 $ 65,195 $ 598 $ 65,793 Consumer mortgage Mortgage Finance 9,753 7 9,760 8,284 10 8,294 Mortgage — Legacy 2,174 81 2,255 2,667 89 2,756 Total consumer mortgage 11,927 88 12,015 10,951 99 11,050 Total consumer $ 78,431 $ 661 $ 79,092 $ 76,146 $ 697 $ 76,843
Schedule Of Pass And Criticized Credit Quality Indicators Of Finance Receivables [Table Text Block]	The following table presents pass and criticized credit quality indicators based on regulatory definitions for our commercial finance receivables and loans recorded at gross carrying value. September 30, 2017 December 31, 2016 ($ in millions) Pass Criticized (a) Total Pass Criticized (a) Total Commercial and industrial Automotive $ 30,189 $ 1,796 $ 31,985 $ 33,160 $ 1,881 $ 35,041 Other 2,913 861 3,774 2,597 651 3,248 Commercial real estate — Automotive 3,891 129 4,020 3,653 159 3,812 Total commercial $ 36,993 $ 2,786 $ 39,779 $ 39,410 $ 2,691 $ 42,101 (a) Includes loans classified as special mention, substandard, or doubtful. These classifications are based on regulatory definitions and generally represent loans within our portfolio that have a higher default risk or have already defaulted.
Impaired Financing Receivables [Table Text Block]	The following table presents information about our impaired finance receivables and loans. ( $ in millions ) Unpaid principal balance (a) Gross carrying value Impaired with no allowance Impaired with an allowance Allowance for impaired loans September 30, 2017 Consumer automotive $ 411 $ 403 $ 86 $ 317 $ 35 Consumer mortgage Mortgage Finance 8 8 4 4 — Mortgage — Legacy 234 229 56 173 30 Total consumer mortgage 242 237 60 177 30 Total consumer 653 640 146 494 65 Commercial Commercial and industrial Automotive 78 78 51 27 3 Other 70 61 10 51 17 Commercial real estate — Automotive 7 7 3 4 1 Total commercial 155 146 64 82 21 Total consumer and commercial finance receivables and loans $ 808 $ 786 $ 210 $ 576 $ 86 December 31, 2016 Consumer automotive $ 407 $ 370 $ 131 $ 239 $ 28 Consumer mortgage Mortgage Finance 8 8 3 5 — Mortgage — Legacy 243 239 56 183 34 Total consumer mortgage 251 247 59 188 34 Total consumer 658 617 190 427 62 Commercial Commercial and industrial Automotive 33 33 7 26 3 Other 99 84 — 84 19 Commercial real estate — Automotive 5 5 2 3 1 Total commercial 137 122 9 113 23 Total consumer and commercial finance receivables and loans $ 795 $ 739 $ 199 $ 540 $ 85 (a) Adjusted for charge-offs.
Schedule of Average Balance And Interest Income Of Impaired Finance Receivables [Table Text Block]	The following tables present average balance and interest income for our impaired finance receivables and loans. 2017 2016 Three months ended September 30, ($ in millions) Average balance Interest income Average balance Interest income Consumer automotive $ 389 $ 5 $ 347 $ 4 Consumer mortgage Mortgage Finance 8 — 8 — Mortgage — Legacy 231 2 245 2 Total consumer mortgage 239 2 253 2 Total consumer 628 7 600 6 Commercial Commercial and industrial Automotive 77 1 48 1 Other 63 — 63 — Commercial real estate — Automotive 7 — 6 — Total commercial 147 1 117 1 Total consumer and commercial finance receivables and loans $ 775 $ 8 $ 717 $ 7 2017 2016 Nine months ended September 30, ($ in millions) Average balance Interest income Average balance Interest income Consumer automotive $ 368 $ 15 $ 340 $ 12 Consumer mortgage Mortgage Finance 8 — 8 — Mortgage — Legacy 236 7 250 7 Total consumer mortgage 244 7 258 7 Total consumer 612 22 598 19 Commercial Commercial and industrial Automotive 55 2 35 1 Other 73 8 58 1 Commercial real estate — Automotive 6 — 6 — Total commercial 134 10 99 2 Total consumer and commercial finance receivables and loans $ 746 $ 32 $ 697 $ 21
Troubled Debt Restructurings on Financing Receivables [Table Text Block]	The following tables present information related to finance receivables and loans recorded at gross carrying value modified in connection with a TDR during the period. 2017 2016 Three months ended September 30, ($ in millions) Number of loans Pre-modification gross carrying value Post-modification gross carrying value Number of loans Pre-modification gross carrying value Post-modification gross carrying value Consumer automotive 7,165 $ 80 $ 75 4,427 $ 70 $ 58 Consumer mortgage Mortgage Finance 2 — — 2 — — Mortgage — Legacy 37 4 4 35 6 6 Total consumer mortgage 39 4 4 37 6 6 Total consumer 7,204 84 79 4,464 76 64 Commercial Commercial and industrial Automotive 3 13 13 — — — Commercial real estate — Automotive 1 3 3 — — — Total commercial 4 16 16 — — — Total consumer and commercial finance receivables and loans 7,208 $ 100 $ 95 4,464 $ 76 $ 64 2017 2016 Nine months ended September 30, ($ in millions) Number of loans Pre-modification gross carrying value Post-modification gross carrying value Number of loans Pre-modification gross carrying value Post-modification gross carrying value Consumer automotive 19,374 $ 298 $ 262 14,816 $ 238 $ 202 Consumer mortgage Mortgage Finance 3 — — 5 2 2 Mortgage — Legacy 109 19 18 92 14 14 Total consumer mortgage 112 19 18 97 16 16 Total consumer 19,486 317 280 14,913 254 218 Commercial Commercial and industrial Automotive 3 13 13 — — — Other 2 44 44 — — — Commercial real estate — Automotive 1 3 3 — — — Total commercial 6 60 60 — — — Total consumer and commercial finance receivables and loans 19,492 $ 377 $ 340 14,913 $ 254 $ 218
Finance receivables and loans redefaulted during the period [Table Text Block]	The following tables present information about finance receivables and loans recorded at gross carrying value that have redefaulted during the reporting period and were within 12 months or less of being modified as a TDR. Redefault is when finance receivables and loans meet the requirements for evaluation under our charge-off policy (refer to Note 1 to the Consolidated Financial Statements in our 2016 Annual Report on Form 10-K for additional information) except for commercial finance receivables and loans, where redefault is defined as 90 days past due. 2017 2016 Three months ended September 30, ($ in millions) Number of loans Gross carrying value Charge-off amount Number of loans Gross carrying value Charge-off amount Consumer automotive 2,222 $ 25 $ 18 1,959 $ 23 $ 14 Consumer mortgage Mortgage Finance — — — — — — Mortgage — Legacy 1 — — 1 — — Total consumer finance receivables and loans 2,223 $ 25 $ 18 1,960 $ 23 $ 14 2017 2016 Nine months ended September 30, ($ in millions) Number of loans Gross carrying value Charge-off amount Number of loans Gross carrying value Charge-off amount Consumer automotive 6,354 $ 74 $ 51 5,617 $ 69 $ 39 Consumer mortgage Mortgage Finance 1 1 — — — — Mortgage — Legacy 1 — — 4 — — Total consumer finance receivables and loans 6,356 $ 75 $ 51 5,621 $ 69 $ 39

Investment in Operating Lease42

Investment in Operating Leases, Net (Tables)	9 Months Ended
	Sep. 30, 2017
Leases, Operating [Abstract]
Schedule of Property Subject to or Available for Operating Lease [Table Text Block]	Investments in operating leases were as follows. ($ in millions) September 30, 2017 December 31, 2016 Vehicles $ 11,001 $ 14,584 Accumulated depreciation (2,070 ) (3,114 ) Investment in operating leases, net $ 8,931 $ 11,470
Depreciation Expense On Operating Lease Assets [Table Text Block]	Depreciation expense on operating lease assets includes remarketing gains and losses recognized on the sale of operating lease assets. The following summarizes the components of depreciation expense on operating lease assets. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Depreciation expense on operating lease assets (excluding remarketing gains) $ 323 $ 470 $ 1,062 $ 1,555 Remarketing gains (51 ) (62 ) (80 ) (203 ) Net depreciation expense on operating lease assets $ 272 $ 408 $ 982 $ 1,352

Securitizations and Variable 43

Securitizations and Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2017
Securitizations And Variable Interest Entities [Abstract]
Schedule of Variable Interest Entities [Table Text Block]	The following table presents our involvement in consolidated and nonconsolidated VIEs in which we hold variable interests. For additional detail related to the assets and liabilities of consolidated variable interest entities refer to the Condensed Consolidated Balance Sheet. ($ in millions) Carrying value of total assets Carrying value of total liabilities Assets sold to nonconsolidated VIEs (a) Maximum exposure to loss in nonconsolidated VIEs September 30, 2017 On-balance sheet variable interest entities Consumer automotive $ 17,462 (b) $ 7,529 (c) Commercial automotive 12,590 2,557 Off-balance sheet variable interest entities Consumer automotive 42 (d) — $ 2,293 $ 2,334 (e) Commercial other 575 (f) 238 (g) — 756 (h) Total $ 30,669 $ 10,324 $ 2,293 $ 3,090 December 31, 2016 On-balance sheet variable interest entities Consumer automotive $ 20,869 (b) $ 8,557 (c) Commercial automotive 16,278 4,764 Off-balance sheet variable interest entities Consumer automotive 24 (f) — $ 2,899 $ 2,923 (e) Commercial other 460 (f) 169 (g) — 651 (h) Total $ 37,631 $ 13,490 $ 2,899 $ 3,574 (a) Asset values represent the current unpaid principal balance of outstanding consumer finance receivables and loans within the VIEs. (b) Includes $8.4 billion and $9.6 billion of assets that are not encumbered by VIE beneficial interests held by third parties at September 30, 2017 , and December 31, 2016 , respectively. Ally or consolidated affiliates hold the interests in these assets. (c) Includes $30 million and $50 million of liabilities that are not obligations to third-party beneficial interest holders at September 30, 2017 , and December 31, 2016 , respectively. (d) Represents retained notes and certificated residual interests, of which $40 million is classified as held-to-maturity securities and $2 million is classified as other assets at September 30, 2017 . These assets represent our compliance with the risk retention rules under the Dodd-Frank Act, requiring us to retain at least five percent of the credit risk of the assets underlying asset-backed securitizations , which became effective on December 24, 2016. (e) Maximum exposure to loss represents the current unpaid principal balance of outstanding loans, retained notes, certificated residual interests, as well as certain noncertificated interests retained from the sale of automotive finance receivables. This measure is based on the very unlikely event that all of our sold loans have defects that would trigger a representation and warranty provision and the underlying collateral supporting the loans becomes worthless. This required disclosure is not an indication of our expected loss. (f) Amounts are classified as other assets. (g) Amounts are classified as accrued expenses and other liabilities. (h) For certain nonconsolidated affordable housing entities, maximum exposure to loss represents the yield we guaranteed investors through long-term guarantee contracts. The amount disclosed is based on the unlikely event that the underlying properties cease generating yield to investors and the yield delivered to investors in the form of low income tax housing credits is recaptured. For nonconsolidated equity investments, maximum exposure to loss represents our outstanding investment, additional committed capital, and low income housing tax credits subject to recapture. The amount disclosed is based on the unlikely event that our committed capital is funded, our investments become worthless, and the tax credits previously delivered to us are recaptured. This required disclosure is not an indication of our expected loss.
Schedule Of Cash Flow Received And Paid To Nonconsolidated Securitization Entities [Table Text Block]	The following table summarizes cash flows received and paid related to securitization entities and asset-backed financings where the transfer is accounted for as a sale and we have a continuing involvement with the transferred assets (e.g., servicing) that were outstanding during the nine months ended September 30, 2017 , and 2016 . Additionally, this table contains information regarding cash flows received from and paid to nonconsolidated securitization entities that existed during each period. Nine months ended September 30, ($ in millions) Consumer automotive 2017 Cash proceeds from transfers completed during the period $ 1,187 Cash disbursements for repurchases during the period (a) (491 ) Servicing fees 25 Cash flows received on retained interests in securitization entities 16 Other cash flows 4 2016 Cash proceeds from transfers completed during the period $ 1,659 Servicing fees 27 Other cash flows 6 (a) During the second quarter of 2017, we elected to not renew a retail automotive credit conduit facility and also purchased the related retail automotive loans and settled associated retained interests.
Schedule of Quantitative Information and Net Credit Losses about Securitized and Other Financial Assets Managed Together [Table Text Block]	The following tables represent on-balance sheet finance receivables and loans, off-balance sheet securitizations, and whole-loan sales where we have continuing involvement. The tables present quantitative information about delinquencies and net credit losses. Total amount Amount 60 days or more past due ($ in millions) September 30, 2017 December 31, 2016 September 30, 2017 December 31, 2016 On-balance sheet finance receivables and loans Consumer automotive $ 67,077 $ 65,793 $ 675 $ 730 Consumer mortgage 12,015 11,050 85 85 Commercial automotive 36,005 38,853 13 7 Commercial other 3,774 3,248 8 — Total on-balance sheet finance receivables and loans 118,871 118,944 781 822 Off-balance sheet securitization entities Consumer automotive 2,293 2,392 14 13 Total off-balance sheet securitization entities 2,293 2,392 14 13 Whole-loan sales (a) 1,655 3,164 4 6 Total $ 122,819 $ 124,500 $ 799 $ 841 (a) Whole-loan sales are not part of a securitization transaction, but represent consumer automotive pools of loans sold to third-party investors. Net credit losses Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 On-balance sheet finance receivables and loans Consumer automotive $ 242 $ 219 $ 692 $ 540 Consumer mortgage 1 (6 ) 3 4 Commercial automotive 1 — 1 — Commercial other 9 — 9 — Total on-balance sheet finance receivables and loans 253 213 705 544 Off-balance sheet securitization entities Consumer automotive 3 2 9 6 Total off-balance sheet securitization entities 3 2 9 6 Whole-loan sales (a) 1 1 3 2 Total $ 257 $ 216 $ 717 $ 552 (a) Whole-loan sales are not part of a securitization transaction, but represent consumer automotive pools of loans sold to third-party investors.

Servicing Activities (Tables)

Servicing Activities (Tables)	9 Months Ended
	Sep. 30, 2017
Servicing Asset [Abstract]
Schedule Of Total Serviced Automobile Loans Outstanding [Table Text Block]	The current unpaid principal balance and any related unamortized deferred fees and costs of total serviced automotive finance loans and leases outstanding were as follows. ($ in millions) September 30, 2017 December 31, 2016 On-balance sheet automotive finance loans and leases Consumer automotive $ 66,721 $ 65,646 Commercial automotive 36,005 38,853 Operating leases 8,853 11,311 Other 71 67 Off-balance sheet automotive finance loans Securitizations 2,312 2,412 Whole-loan sales 1,668 3,191 Total serviced automotive finance loans and leases $ 115,630 $ 121,480

Other Assets (Tables)

Other Assets (Tables)	9 Months Ended
	Sep. 30, 2017
Other Assets [Abstract]
Schedule of Other Assets [Table Text Block]	The components of other assets were as follows. ($ in millions) September 30, 2017 December 31, 2016 Property and equipment at cost $ 1,024 $ 901 Accumulated depreciation (587 ) (525 ) Net property and equipment 437 376 Restricted cash collections for securitization trusts (a) 1,260 1,694 Nonmarketable equity investments (b) 1,065 1,046 Net deferred tax assets 659 994 Accrued interest and rent receivables 508 476 Goodwill (c) 240 240 Other accounts receivable 212 100 Cash reserve deposits held for securitization trusts (d) 120 184 Restricted cash and cash equivalents 112 111 Fair value of derivative contracts in receivable position (e) 37 95 Cash collateral placed with counterparties 20 167 Other assets 1,393 1,371 Total other assets $ 6,063 $ 6,854 (a) Represents cash collections from customer payments on securitized receivables. These funds are distributed to investors as payments on the related secured debt. (b) Includes investments in FHLB stock of $581 million and $577 million at September 30, 2017 , and December 31, 2016 , respectively; and Federal Reserve Bank (FRB) stock of $445 million and $435 million at September 30, 2017 , and December 31, 2016 , respectively. (c) Includes goodwill of $27 million within our Insurance operations at both September 30, 2017 , and December 31, 2016 ; $193 million within Corporate and Other at both September 30, 2017 , and December 31, 2016 ; and $20 million within Automotive Finance operations at both September 30, 2017 , and December 31, 2016 . No changes to the carrying amount of goodwill were recorded during the nine months ended September 30, 2017 . (d) Represents credit enhancement in the form of cash reserves for various securitization transactions. (e) For additional information on derivative instruments and hedging activities, refer to Note 19 .

Deposit Liabilities (Tables)

Deposit Liabilities (Tables)	9 Months Ended
	Sep. 30, 2017
Deposits [Abstract]
Schedule of Deposit Liabilities [Table Text Block]	Deposit liabilities consisted of the following. ( $ in millions ) September 30, 2017 December 31, 2016 Noninterest-bearing deposits $ 129 $ 84 Interest-bearing deposits Savings and money market checking accounts 50,287 46,976 Certificates of deposit 39,686 31,795 Dealer deposits 14 167 Total deposit liabilities $ 90,116 $ 79,022

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule of Short-term Debt [Table Text Block]	The following table presents the composition of our short-term borrowings portfolio. September 30, 2017 December 31, 2016 ($ in millions) Unsecured Secured (a) Total Unsecured Secured (a) Total Demand notes $ 3,379 $ — $ 3,379 $ 3,622 $ — $ 3,622 Federal Home Loan Bank — 5,625 5,625 — 7,875 7,875 Financial instruments sold under agreements to repurchase — 1,171 1,171 — 1,176 1,176 Total short-term borrowings $ 3,379 $ 6,796 $ 10,175 $ 3,622 $ 9,051 $ 12,673 (a) Refer to the section below titled Long-term Debt for further details on assets restricted as collateral for payment of the related debt.
Schedule of Debt [Table Text Block]	The following table presents the composition of our long-term debt portfolio. September 30, 2017 December 31, 2016 ($ in millions) Unsecured Secured Total Unsecured Secured Total Long-term debt Due within one year $ 3,828 $ 6,642 $ 10,470 $ 4,274 $ 10,279 $ 14,553 Due after one year (a) 13,129 21,249 34,378 15,450 23,810 39,260 Fair value adjustment (b) 289 (15 ) 274 326 (11 ) 315 Total long-term debt (c) $ 17,246 $ 27,876 $ 45,122 $ 20,050 $ 34,078 $ 54,128 (a) Includes $2.6 billion of trust preferred securities at both September 30, 2017 , and December 31, 2016 . (b) Represents the fair value adjustment associated with the application of hedge accounting on certain of our long-term debt positions. Refer to Note 19 for additional information. (c) Includes advances from the FHLB of Pittsburgh of $8.4 billion and $6.1 billion at September 30, 2017 , and December 31, 2016 , respectively.
Scheduled Remaining Maturity of Long-term Debt [Table Text Block]	The following table presents the scheduled remaining maturity of long-term debt at September 30, 2017 , assuming no early redemptions will occur. The actual payment of secured debt may vary based on the payment activity of the related pledged assets. ($ in millions) 2017 2018 2019 2020 2021 2022 and thereafter Fair value adjustment Total Unsecured Long-term debt $ 1,590 $ 3,582 $ 1,680 $ 2,252 $ 637 $ 8,475 $ 289 $ 18,505 Original issue discount (24 ) (100 ) (39 ) (39 ) (43 ) (1,014 ) — (1,259 ) Total unsecured 1,566 3,482 1,641 2,213 594 7,461 289 17,246 Secured Long-term debt 1,048 7,379 7,617 6,818 3,179 1,850 (15 ) 27,876 Total long-term debt $ 2,614 $ 10,861 $ 9,258 $ 9,031 $ 3,773 $ 9,311 $ 274 $ 45,122
Pledged assets for the payment of the related secured borrowings and repurchase agreements [Table Text Block]	The following summarizes assets restricted as collateral for the payment of the related debt obligation primarily arising from securitization transactions accounted for as secured borrowings and repurchase agreements. September 30, 2017 December 31, 2016 ($ in millions) Total (a) Ally Bank Total (a) Ally Bank Investment securities (b) $ 6,676 $ 5,482 $ 4,895 $ 4,231 Mortgage assets held-for-investment and lending receivables 11,888 11,888 10,954 10,954 Consumer automotive finance receivables (b) 21,261 4,818 27,846 5,751 Commercial automotive finance receivables 16,142 16,018 19,487 19,280 Investment in operating leases, net 737 7 2,040 913 Total assets restricted as collateral (c) (d) $ 56,704 $ 38,213 $ 65,222 $ 41,129 Secured debt $ 34,672 (e) $ 18,781 $ 43,129 (e) $ 22,149 (a) Ally Bank is a component of the total column. (b) A portion of the restricted investment securities at September 30, 2017 , and December 31, 2016 , and consumer automotive finance receivables at December 31, 2016 , were restricted under repurchase agreements. Refer to the section above titled Short-term Borrowings for information on the repurchase agreements. (c) Ally Bank has an advance agreement with the FHLB, and had assets pledged to secure borrowings that were restricted as collateral to the FHLB totaling $21.4 billion and $19.0 billion at September 30, 2017 , and December 31, 2016 , respectively. These assets were composed primarily of consumer mortgage finance receivables and loans and investment securities. Ally Bank has access to the FRB Discount Window. Ally Bank had assets pledged and restricted as collateral to the FRB totaling $2.3 billion and $2.4 billion at September 30, 2017 , and December 31, 2016 , respectively. These assets were composed of consumer automotive finance receivables and loans and operating lease assets. Availability under these programs is only for the operations of Ally Bank and cannot be used to fund the operations or liabilities of Ally or its subsidiaries. (d) Excludes restricted cash and cash reserves for securitization trusts recorded within other assets on the Condensed Consolidated Balance Sheet . Refer to Note 12 for additional information. (e) Includes $6.8 billion and $9.1 billion of short-term borrowings at September 30, 2017 , and December 31, 2016 , respectively.
Schedule Of Committed Funding Facilities [Table Text Block]	Committed Funding Facilities Outstanding Unused capacity (a) Total capacity ($ in millions) September 30, 2017 December 31, 2016 September 30, 2017 December 31, 2016 September 30, 2017 December 31, 2016 Bank funding Secured (b) $ 1,350 $ 3,250 $ 2,325 $ 350 $ 3,675 $ 3,600 Parent funding Secured 8,180 11,550 2,820 1,975 11,000 13,525 Unsecured — — — 1,250 — 1,250 Total committed facilities $ 9,530 $ 14,800 $ 5,145 $ 3,575 $ 14,675 $ 18,375 (a) Funding from committed secured facilities is available on request in the event excess collateral resides in certain facilities or the extent incremental collateral is available and contributed to the facilities. (b) Excludes off-balance sheet credit facility amounts.

Accrued Expenses and Other Li48

Accrued Expenses and Other Liabilities (Tables)	9 Months Ended
	Sep. 30, 2017
Accounts Payable and Accrued Liabilities [Abstract]
Schedule of Accrued Liabilities [Table Text Block]	The components of accrued expenses and other liabilities were as follows. ( $ in millions ) September 30, 2017 December 31, 2016 Accounts payable $ 863 $ 649 Employee compensation and benefits 227 232 Reserves for insurance losses and loss adjustment expenses 173 149 Deferred revenue 34 56 Fair value of derivative contracts in payable position (a) 30 95 Cash collateral received from counterparties 14 10 Other liabilities 551 546 Total accrued expenses and other liabilities $ 1,892 $ 1,737 (a) For additional information on derivative instruments and hedging activities, refer to Note 19 .

Accumulated Other Comprehensi49

Accumulated Other Comprehensive (Loss) Income (Tables)	9 Months Ended
	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table presents changes, net of tax, in each component of accumulated other comprehensive (loss) income. ($ in millions) Unrealized (losses) gains on investment securities (a) Translation adjustments and net investment hedges (b) Cash flow hedges (b) Defined benefit pension plans Accumulated other comprehensive (loss) income Balance at December 31, 2015 $ (159 ) $ 9 $ 8 $ (89 ) $ (231 ) 2016 net change 258 5 — (1 ) 262 Balance at September 30, 2016 $ 99 $ 14 $ 8 $ (90 ) $ 31 Balance at December 31, 2016 $ (273 ) $ 14 $ 8 $ (90 ) $ (341 ) 2017 net change 142 2 1 (1 ) 144 Balance at September 30, 2017 $ (131 ) $ 16 $ 9 $ (91 ) $ (197 ) (a) Represents the after-tax difference between the fair value and amortized cost of our available-for-sale securities portfolio. (b) For additional information on derivative instruments and hedging activities, refer to Note 19 .
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The following tables present the before- and after-tax changes in each component of accumulated other comprehensive (loss) income. Three months ended September 30, 2017 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 95 $ (22 ) $ 73 Less: Net realized gains reclassified to income from continuing operations 25 (a) 2 (b) 27 Net change 70 (24 ) 46 Translation adjustments Net unrealized gains arising during the period 8 (3 ) 5 Net investment hedges (c) Net unrealized losses arising during the period (6 ) 3 (3 ) Cash flow hedges (c) Net unrealized gains arising during the period 1 (1 ) — Other comprehensive income $ 73 $ (25 ) $ 48 (a) Includes gains reclassified to other gain on investments, net in our Condensed Consolidated Statement of Comprehensive Income . (b) Includes amounts reclassified to income tax expense from continuing operations in our Condensed Consolidated Statement of Comprehensive Income . (c) For additional information on derivative instruments and hedging activities, refer to Note 19 . Three months ended September 30, 2016 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 41 $ (4 ) $ 37 Less: Net realized gains reclassified to income from continuing operations 52 (a) (11 ) (b) 41 Net change (11 ) 7 (4 ) Translation adjustments Net unrealized losses arising during the period (2 ) 1 (1 ) Net investment hedges (c) Net unrealized gains arising during the period 2 (1 ) 1 Other comprehensive income $ (11 ) $ 7 $ (4 ) (a) Includes gains reclassified to other gain on investments, net in our Condensed Consolidated Statement of Comprehensive Income . (b) Includes amounts reclassified to income tax expense from continuing operations in our Condensed Consolidated Statement of Comprehensive Income . (c) For additional information on derivative instruments and hedging activities, refer to Note 19 . Nine months ended September 30, 2017 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 278 $ (64 ) $ 214 Less: Net realized gains reclassified to income from continuing operations 75 (a) (3 ) (b) 72 Net change 203 (61 ) 142 Translation adjustments Net unrealized gains arising during the period 14 (5 ) 9 Net investment hedges (c) Net unrealized losses arising during the period (12 ) 5 (7 ) Cash flow hedges (c) Net unrealized gains arising during the period 2 (1 ) 1 Defined benefit pension plans Net unrealized losses arising during the period (1 ) — (1 ) Other comprehensive income $ 206 $ (62 ) $ 144 (a) Includes gains reclassified to other gain on investments, net in our Condensed Consolidated Statement of Comprehensive Income . (b) Includes amounts reclassified to income tax expense from continuing operations in our Condensed Consolidated Statement of Comprehensive Income . (c) For additional information on derivative instruments and hedging activities, refer to Note 19 . Nine months ended September 30, 2016 ($ in millions) Before Tax Tax Effect After Tax Investment securities Net unrealized gains arising during the period $ 506 $ (133 ) $ 373 Less: Net realized gains reclassified to income from continuing operations 145 (a) (30 ) (b) 115 Net change 361 (103 ) 258 Translation adjustments Net unrealized gains arising during the period 10 (4 ) 6 Less: Net realized losses reclassified to income from discontinued operations, net of tax (1 ) — (1 ) Net change 11 (4 ) 7 Net investment hedges (c) Net unrealized losses arising during the period (4 ) 2 (2 ) Defined benefit pension plans Net unrealized losses arising during the period (1 ) — (1 ) Other comprehensive income $ 367 $ (105 ) $ 262 (a) Includes gains reclassified to other gain on investments, net in our Condensed Consolidated Statement of Comprehensive Income . (b) Includes amounts reclassified to income tax expense from continuing operations in our Condensed Consolidated Statement of Comprehensive Income . (c) For additional information on derivative instruments and hedging activities, refer to Note 19 .

Earnings per Common Share (Tabl

Earnings per Common Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table presents the calculation of basic and diluted earnings per common share. Three months ended September 30, Nine months ended September 30, ($ in millions, except per share data; shares in thousands) (a) 2017 2016 2017 2016 Net income from continuing operations $ 280 $ 261 $ 747 $ 865 Preferred stock dividends — — — (30 ) Net income from continuing operations attributable to common shareholders 280 261 747 835 Income (loss) from discontinued operations, net of tax 2 (52 ) 1 (46 ) Net income attributable to common shareholders $ 282 $ 209 $ 748 $ 789 Basic weighted-average common shares outstanding (b) 449,169 482,393 457,612 483,993 Diluted weighted-average common shares outstanding (b) 451,078 483,575 458,848 484,762 Basic earnings per common share Net income from continuing operations $ 0.62 $ 0.54 $ 1.63 $ 1.73 Income (loss) from discontinued operations, net of tax — (0.11 ) — (0.10 ) Net income $ 0.63 $ 0.43 $ 1.63 $ 1.63 Diluted earnings per common share Net income from continuing operations $ 0.62 $ 0.54 $ 1.63 $ 1.72 Income (loss) from discontinued operations, net of tax — (0.11 ) — (0.10 ) Net income $ 0.63 $ 0.43 $ 1.63 $ 1.63 (a) Figures in the table may not recalculate exactly due to rounding. Earnings per share is calculated based on unrounded numbers. (b) Includes shares related to share-based compensation that vested but were not yet issued for the three months and nine months ended September 30, 2017 , and 2016 .

Regulatory Capital and Other 51

Regulatory Capital and Other Regulatory Matters (Tables)	9 Months Ended
	Sep. 30, 2017
Regulatory Capital Requirements [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block]	The following table summarizes our capital ratios under the U.S. Basel III capital framework. September 30, 2017 December 31, 2016 Required minimum Well-capitalized minimum ( $ in millions ) Amount Ratio Amount Ratio Capital ratios Common Equity Tier 1 (to risk-weighted assets) Ally Financial Inc. $ 13,175 9.72 % $ 12,978 9.37 % 4.50 % (a) Ally Bank 16,454 15.39 17,888 16.70 4.50 6.50 % Tier 1 (to risk-weighted assets) Ally Financial Inc. $ 15,539 11.46 % $ 15,147 10.93 % 6.00 % 6.00 % Ally Bank 16,454 15.39 17,888 16.70 6.00 8.00 Total (to risk-weighted assets) Ally Financial Inc. $ 17,891 13.19 % $ 17,419 12.57 % 8.00 % 10.00 % Ally Bank 17,215 16.10 18,458 17.24 8.00 10.00 Tier 1 leverage (to adjusted quarterly average assets) (b) Ally Financial Inc. $ 15,539 9.51 % $ 15,147 9.54 % 4.00 % (a) Ally Bank 16,454 12.89 17,888 15.21 4.00 (c) 5.00 % (a) Currently, there is no ratio component for determining whether a BHC is "well-capitalized." (b) Federal regulatory reporting guidelines require the calculation of adjusted quarterly average assets using a daily average methodology. (c) On August 22, 2017, the FRB lifted the capital, liquidity, and business plan commitments that Ally Bank made in connection with its application for membership in the Federal Reserve System, including the commitment to maintain a Tier 1 leverage ratio of at least 15% . Ally Bank now manages its capital and liquidity subject to applicable regulatory requirements.
Schedule of Common Share Repurchase Activity [Table Text Block]	The following table presents information related to our common shares for each quarter since the commencement of our common share repurchase programs and initiation of a quarterly cash dividend on common stock. ($ in millions, except per share data; shares in thousands) 3rd quarter 2017 2nd quarter 2017 1st quarter 2017 4th quarter 2016 3rd quarter 2016 Common shares repurchased during period (a) Approximate dollar value $ 190 $ 204 $ 169 $ 167 $ 159 Number of shares 8,507 10,485 8,097 8,745 8,298 Number of common shares outstanding Beginning of period 452,292 462,193 467,000 475,470 483,753 End of period 443,796 452,292 462,193 467,000 475,470 Cash dividends declared per common share (b) $ 0.12 $ 0.08 $ 0.08 $ 0.08 $ 0.08 (a) Includes shares of common stock withheld to cover income taxes owed by participants in our share-based incentive plans. (b) On October 10, 2017 , the Ally Board of Directors declared a quarterly cash dividend payment of $0.12 per share on all common stock, payable on November 15, 2017 . Refer to Note 26 for further information regarding this common share dividend.

Derivative Instruments and He52

Derivative Instruments and Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Value Amounts of Derivative Instruments Reported On Our Condensed Consolidated Balance Sheet [Table Text Block]	The following table summarizes the fair value amounts of derivative instruments reported on our Condensed Consolidated Balance Sheet . The fair value amounts are presented on a gross basis, are segregated by derivatives that are designated and qualifying as hedging instruments or those that are not, and are further segregated by type of contract within those two categories. Notional amounts are reference amounts from which contractual obligations are derived and are not recorded on the balance sheet. In our view, derivative notional is not an accurate measure of our derivative exposure when viewed in isolation from other factors, such as market rate fluctuations and counterparty credit risk. September 30, 2017 December 31, 2016 Derivative contracts in a Notional amount Derivative contracts in a Notional amount ($ in millions) receivable position (a) payable position (b) receivable position (a) payable position (b) Derivatives designated as accounting hedges Interest rate contracts Swaps (c) (d) (e) (f) (g) $ — $ — $ 6,140 $ 19 $ 21 $ 4,731 Futures (h) 1 — 60 — — — Foreign exchange contracts Forwards 3 — 176 1 — 171 Total derivatives designated as accounting hedges 4 — 6,376 20 21 4,902 Derivatives not designated as accounting hedges Interest rate contracts Swaps — — — — — 137 Futures and forwards — — 116 — — — Written options 1 30 9,452 — 73 14,518 Purchased options 30 — 9,335 73 — 14,517 Total interest rate risk 31 30 18,903 73 73 29,172 Foreign exchange contracts Futures and forwards 2 — 130 1 — 92 Total foreign exchange risk 2 — 130 1 — 92 Equity contracts Written options — — — — 1 — Purchased options — — — 1 — — Total equity risk — — — 1 1 — Total derivatives not designated as accounting hedges 33 30 19,033 75 74 29,264 Total derivatives $ 37 $ 30 $ 25,409 $ 95 $ 95 $ 34,166 (a) Derivative contracts in a receivable position are classified as other assets on the Condensed Consolidated Balance Sheet , and include accrued interest of $0 million and $7 million at September 30, 2017 , and December 31, 2016 , respectively. (b) Derivative contracts in a liability position are classified as accrued expenses and other liabilities on the Condensed Consolidated Balance Sheet , and include accrued interest of $0 million and $1 million at September 30, 2017 , and December 31, 2016 , respectively. (c) Includes fair value hedges consisting of receive-fixed swaps on fixed-rate unsecured debt obligations with $0 million and $8 million in a receivable position, $0 million and $14 million in a payable position, and a $3.1 billion and $1.7 billion notional amount at September 30, 2017 , and December 31, 2016 , respectively. The hedge notional amount of $3.1 billion at September 30, 2017 , is associated with debt maturing in approximately five or more years. (d) Includes fair value hedges consisting of receive-fixed swaps on fixed-rate secured debt obligations (FHLB advances) with $0 million and $0 million in a receivable position, $0 million and $7 million in a payable position, and a $1.6 billion and $240 million notional amount at September 30, 2017 , and December 31, 2016 , respectively. Other fair value hedges include pay-fixed swaps on portfolios of held-for-investment automotive loan assets with $0 million and $10 million in a receivable position, $0 million and $1 million in a payable position, and a $0.0 billion and $2.8 billion notional amount at September 30, 2017 , and December 31, 2016 , respectively. (e) Includes cash flow hedge of pay-fixed swap on variable-rate borrowings of a secured credit facility with $0 million in a receivable and payable position, and $1.3 billion of notional amount at September 30, 2017 . (f) Includes fair value hedge of pay-fixed swaps on fixed-rate U.S. Treasury securities with $0 million in a receivable and payable position, and $225 million of notional amount at September 30, 2017 . (g) Derivative contracts in a receivable and payable position exclude open trade equity on derivatives cleared through central clearing counterparties. Any associated collateral exchanged with our central clearing counterparties are treated as settlements of the derivative exposure, rather than collateral. Such payments are recognized as settlements of the derivatives contracts in a receivable and payable position in our Condensed Consolidated Balance Sheet. (h) Includes fair value hedge of future contract on fixed-rate U.S. Treasury securities with $1 million in a receivable position, $0 million in a payable position, and $60 million of notional amount at September 30, 2017
Gains and Losses On Derivative Instruments Reported in Statement of Comprehensive Income [Table Text Block]	The following table summarizes the location and amounts of gains and losses on derivative instruments reported in our Condensed Consolidated Statement of Comprehensive Income . Three months ended September 30, Nine months ended September 30, ( $ in millions ) 2017 2016 2017 2016 Derivatives qualifying for hedge accounting Gain (loss) recognized in earnings on derivatives Interest rate contracts Interest and fees on finance receivables and loans (a) $ — $ 16 $ 1 $ (18 ) Interest and dividends on investment securities 4 — 1 — Interest on long-term debt (b) (5 ) (31 ) 19 211 (Loss) gain recognized in earnings on hedged items Interest rate contracts Interest and fees on finance receivables and loans (c) — (17 ) (3 ) 16 Interest and dividends on investment securities (4 ) — (1 ) — Interest on long-term debt (d) 5 32 (18 ) (214 ) Total derivatives qualifying for hedge accounting — — (1 ) (5 ) Derivatives not designated as accounting hedges Gain (loss) recognized in earnings on derivatives Interest rate contracts Gain on mortgage and automotive loans, net — — 1 — Other income, net of losses — (5 ) (3 ) (2 ) Total interest rate contracts — (5 ) (2 ) (2 ) Foreign exchange contracts (e) Interest on long-term debt — — — (2 ) Other income, net of losses (3 ) (1 ) (7 ) (4 ) Total foreign exchange contracts (3 ) (1 ) (7 ) (6 ) Equity contracts Compensation and benefits expense — 2 — — Total equity contracts — 2 — — Loss recognized in earnings on derivatives $ (3 ) $ (4 ) $ (10 ) $ (13 ) (a) Amounts exclude losses related to interest for qualifying accounting hedges of retail automotive loans held-for-investment, which are primarily offset by the fixed coupon payments of the loans. The losses were $0 million and $4 million for the three months ended September 30, 2017 , and 2016 , respectively, and $1 million and $16 million for the nine months ended September 30, 2017 , and 2016 , respectively. (b) Amounts exclude gains related to interest for qualifying accounting hedges of unsecured debt, which are primarily offset by the fixed coupon payment on the long-term debt. The gains were $7 million for both the three months ended September 30, 2017 , and 2016, and $19 million and $34 million for the nine months ended September 30, 2017 , and 2016 , respectively. Amounts also exclude gains related to interest for qualifying accounting hedges of secured debt (FHLB advances), which are primarily offset by the fixed coupon payment on the long-term debt. The gains were $0 million and $1 million for the three months ended September 30, 2017 , and 2016, respectively, and $1 million and $4 million for the nine months ended September 30, 2017 , and 2016 , respectively. (c) Amounts exclude losses related to amortization of deferred loan basis adjustments on the de-designated hedged item of $6 million for both the three months ended September 30, 2017 , and 2016 , and $17 million and $15 million for the nine months ended September 30, 2017 , and 2016 , respectively. (d) Amounts exclude gains related to amortization of deferred debt basis adjustments on the de-designated hedged item of $19 million and $23 million for the three months ended September 30, 2017 , and 2016 , respectively, and $59 million and $62 million for the nine months ended September 30, 2017 , and 2016 , respectively. Amounts also exclude losses related to amortization of deferred debt basis adjustments (FHLB advances) on the de-designated hedge item of $1 million for the three months ended September 30, 2017 , and $2 million for the nine months ended September 30, 2017 . (e) Amounts exclude gains and losses related to the revaluation of the related foreign-denominated debt or receivable. Gains of $3 million and $1 million were recognized for the three months ended September 30, 2017 , and 2016 , respectively, and gains of $8 million and $4 million were recognized for the nine months ended September 30, 2017 , and 2016 , respectively.
Derivative Instruments Used in Cash Flow and Net Investment Hedge Accounting Relationships [Table Text Block]	The following table summarizes derivative instruments used in cash flow and net investment hedge accounting relationships. Three months ended September 30, Nine months ended September 30, ($ in millions) 2017 2016 2017 2016 Cash flow hedges Interest rate contracts Gain recognized in other comprehensive loss $ 2 $ — $ 2 $ — Net investment hedges Foreign exchange contracts (Loss) gain recognized in other comprehensive loss (a) $ (6 ) $ 2 $ (12 ) $ (4 ) (a) The amounts represent the effective portion of net investment hedges. There are offsetting amounts recognized in accumulated other comprehensive loss related to the revaluation of the related net investment in foreign operations, including the tax impacts of the hedge and related net investment, as disclosed separately in Note 16 . There were gains of $7 million and losses of $2 million for the three months ended September 30, 2017 , and 2016 , respectively, and gains of $14 million and $9 million for the nine months ended September 30, 2017, and 2016.

Fair Value (Tables)

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements - Recurring Basis [Table Text Block]	The following tables display the assets and liabilities measured at fair value on a recurring basis including financial instruments elected for the fair value option. We often economically hedge the fair value change of our assets or liabilities with derivatives and other financial instruments. The tables below display the hedges separately from the hedged items; therefore, they do not directly display the impact of our risk management activities. Recurring fair value measurements September 30, 2017 ($ in millions) Level 1 Level 2 Level 3 Total Assets Investment securities Available-for-sale securities Debt securities U.S. Treasury $ 2,073 $ — $ — $ 2,073 U.S. States and political subdivisions — 851 — 851 Foreign government 8 149 — 157 Agency mortgage-backed residential — 14,344 — 14,344 Mortgage-backed residential — 2,310 — 2,310 Mortgage-backed commercial — 509 — 509 Asset-backed — 1,039 — 1,039 Corporate debt — 1,291 — 1,291 Total debt securities 2,081 20,493 — 22,574 Equity securities (a) 525 — — 525 Total available-for-sale securities 2,606 20,493 — 23,099 Mortgage loans held-for-sale — — 9 9 Interests retained in financial asset sales — — 5 5 Derivative contracts in a receivable position Interest rate 1 30 1 32 Foreign currency — 5 — 5 Total derivative contracts in a receivable position 1 35 1 37 Total assets $ 2,607 $ 20,528 $ 15 $ 23,150 Liabilities Accrued expenses and other liabilities Derivative contracts in a payable position Interest rate $ — $ (30 ) $ — $ (30 ) Total derivative contracts in a payable position — (30 ) — (30 ) Total liabilities $ — $ (30 ) $ — $ (30 ) (a) Our investment in any one industry did not exceed 15% . Recurring fair value measurements December 31, 2016 ($ in millions) Level 1 Level 2 Level 3 Total Assets Investment securities Available-for-sale securities Debt securities U.S. Treasury $ 1,620 $ — $ — $ 1,620 U.S. States and political subdivisions — 782 — 782 Foreign government 11 151 — 162 Agency mortgage-backed residential — 10,290 — 10,290 Mortgage-backed residential — 2,097 — 2,097 Mortgage-backed commercial — 537 — 537 Asset-backed — 1,400 — 1,400 Corporate debt — 1,443 — 1,443 Total debt securities 1,631 16,700 — 18,331 Equity securities (a) 595 — — 595 Total available-for-sale securities 2,226 16,700 — 18,926 Other assets Interests retained in financial asset sales — — 29 29 Derivative contracts in a receivable position Interest rate — 92 — 92 Foreign currency — 2 — 2 Other 1 — — 1 Total derivative contracts in a receivable position 1 94 — 95 Total assets $ 2,227 $ 16,794 $ 29 $ 19,050 Liabilities Accrued expenses and other liabilities Derivative contracts in a payable position Interest rate $ — $ (94 ) $ — $ (94 ) Other (1 ) — — (1 ) Total derivative contracts in a payable position (1 ) (94 ) — (95 ) Total liabilities $ (1 ) $ (94 ) $ — $ (95 ) (a) Our investment in any one industry did not exceed 14% .
Fair Value Measurements - Reconciliation of Level 3 Assets and Liabilities [Table Text Block]	The following tables present the reconciliation for all Level 3 assets and liabilities measured at fair value on a recurring basis. We often economically hedge the fair value change of our assets or liabilities with derivatives and other financial instruments. The Level 3 items presented below may be hedged by derivatives and other financial instruments that are classified as Level 1 or Level 2. Thus, the following tables do not fully reflect the impact of our risk management activities. Level 3 recurring fair value measurements Net realized/unrealized gains Fair value at September 30, 2017 Net unrealized gains included in earnings still held at September 30, 2017 ($ in millions) Fair value at July 1, 2017 included in earnings included in OCI Purchases Sales Issuances Settlements Assets Mortgage loans held-for-sale $ 3 $ 1 $ — $ 49 $ (44 ) $ — $ — $ 9 $ — Other assets Interests retained in financial asset sales 5 — — — — — — 5 — Derivative assets 1 — — — — — — 1 — Total assets $ 9 $ 1 $ — $ 49 $ (44 ) $ — $ — $ 15 $ — Level 3 recurring fair value measurements Fair value at July 1, 2016 Net realized/unrealized gains Purchases Sales Issuances Settlements Fair value at September 30, 2016 Net unrealized gains included in earnings still held at September 30, 2016 ($ in millions) included in earnings included in OCI Assets Other assets Interests retained in financial asset sales $ 31 $ 1 (a) $ — $ — $ 2 $ — $ (2 ) $ 32 $ — Total assets $ 31 $ 1 $ — $ — $ 2 $ — $ (2 ) $ 32 $ — (a) Reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income . Level 3 recurring fair value measurements Net realized/unrealized gains Fair value at September 30, 2017 Net unrealized gains included in earnings still held at September 30, 2017 ($ in millions) Fair value at Jan. 1, 2017 included in earnings included in OCI Purchases Sales Issuances Settlements Assets Mortgage loans held-for-sale $ — $ 1 $ — $ 72 $ (64 ) $ — $ — $ 9 $ — Other assets Interests retained in financial asset sales 29 1 — — 8 — (33 ) 5 — Derivative assets — 1 — — — — — 1 1 Total assets $ 29 $ 3 $ — $ 72 $ (56 ) $ — $ (33 ) $ 15 $ 1 Level 3 recurring fair value measurements Fair value at Jan. 1, 2016 Net realized/unrealized gains Purchases Sales Issuances Settlements Fair value at September 30, 2016 Net unrealized gains included in earnings still held at September 30, 2016 ($ in millions) included in earnings included in OCI Assets Other assets Interests retained in financial asset sales $ 40 $ 4 (a) $ — $ — $ 8 $ — $ (20 ) $ 32 $ — Total assets $ 40 $ 4 $ — $ — $ 8 $ — $ (20 ) $ 32 $ — (a) Reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income .
Fair Value Measurements - Nonrecurring Basis [Table Text Block]	The following tables display the assets and liabilities measured at fair value on a nonrecurring basis. Nonrecurring fair value measurements Lower-of-cost or fair value or valuation reserve allowance Total gain (loss) included in earnings for the three months ended Total gain (loss) included in earnings for the nine months ended September 30, 2017 ($ in millions) Level 1 Level 2 Level 3 Total Assets Loans held-for-sale, net $ — $ — $ 9 $ 9 $ — n/m (a) n/m (a) Commercial finance receivables and loans, net (b) Automotive — — 29 29 $ (4 ) n/m (a) n/m (a) Other — — 35 35 (16 ) n/m (a) n/m (a) Total commercial finance receivables and loans, net — — 64 64 (20 ) n/m (a) n/m (a) Other assets Repossessed and foreclosed assets (c) — — 13 13 (2 ) n/m (a) n/m (a) Other — — 3 3 — n/m (a) n/m (a) Total assets $ — $ — $ 89 $ 89 $ (22 ) n/m n/m n/m = not meaningful (a) We consider the applicable valuation or loan loss allowance to be the most relevant indicator of the impact on earnings caused by the fair value measurement. Accordingly, the table above excludes total gains and losses included in earnings for these items. The carrying values are inclusive of the respective valuation or loan loss allowance. (b) Represents the portion of the portfolio specifically impaired during 2017. The related valuation allowance represents the cumulative adjustment to fair value of those specific receivables. (c) The allowance provided for repossessed and foreclosed assets represents any cumulative valuation adjustment recognized to adjust the assets to fair value. Nonrecurring fair value measurements Lower-of-cost or fair value or valuation reserve allowance Total gain included in earnings for the three months ended Total gain included in earnings for the nine months ended September 30, 2016 ($ in millions) Level 1 Level 2 Level 3 Total Assets Loans held-for-sale, net $ — $ — $ 56 $ 56 $ — n/m (a) n/m (a) Commercial finance receivables and loans, net (b) Commercial and industrial Automotive — — 30 30 (7 ) n/m (a) n/m (a) Other — — 45 45 (17 ) n/m (a) n/m (a) Total commercial finance receivables and loans, net — — 75 75 (24 ) n/m (a) n/m (a) Other assets Repossessed and foreclosed assets (c) — — 15 15 (4 ) n/m (a) n/m (a) Other — — 7 7 — n/m (a) n/m (a) Total assets $ — $ — $ 153 $ 153 $ (28 ) n/m n/m n/m = not meaningful (a) We consider the applicable valuation or loan loss allowance to be the most relevant indicator of the impact on earnings caused by the fair value measurement. Accordingly, the table above excludes total gains and losses included in earnings for these items. The carrying values are inclusive of the respective valuation or loan loss allowance. (b) Represents the portion of the portfolio specifically impaired during 2016 . The related valuation allowance represents the cumulative adjustment to fair value of those specific receivables. (c) The allowance provided for repossessed and foreclosed assets represents any cumulative valuation adjustment recognized to adjust the assets to fair value.
Fair Value of Financial Intruments [Table Text Block]	The following table presents the carrying and estimated fair value of financial instruments, except for those recorded at fair value on a recurring basis presented in the previous section of this note titled Recurring Fair Value. When possible, we use quoted market prices to determine fair value. Where quoted market prices are not available, the fair value is internally derived based on appropriate valuation methodologies with respect to the amount and timing of future cash flows and estimated discount rates. However, considerable judgment is required in interpreting current market data to develop the market assumptions and inputs necessary to estimate fair value. As such, the actual amount received to sell an asset or the amount paid to settle a liability could differ from our estimates. Fair value information presented herein was based on information available at September 30, 2017 , and December 31, 2016 . Estimated fair value ($ in millions) Carrying value Level 1 Level 2 Level 3 Total September 30, 2017 Financial assets Held-to-maturity securities $ 1,839 $ — $ 1,807 $ — $ 1,807 Loans held-for-sale, net 9 — — 9 9 Finance receivables and loans, net 117,585 — — 119,498 119,498 Nonmarketable equity investments (a) 1,053 — 1,026 26 1,052 Financial liabilities Deposit liabilities $ 90,116 $ — $ — $ 88,151 $ 88,151 Short-term borrowings 10,175 — — 10,177 10,177 Long-term debt 45,122 — 29,776 17,880 47,656 December 31, 2016 Financial assets Held-to-maturity securities $ 839 $ — $ 789 $ — $ 789 Finance receivables and loans, net 117,800 — — 118,750 118,750 Nonmarketable equity investments 1,046 — 1,012 55 1,067 Financial liabilities Deposit liabilities $ 79,022 $ — $ — $ 78,469 $ 78,469 Short-term borrowings 12,673 — — 12,675 12,675 Long-term debt 54,128 — 22,036 34,084 56,120 (a) Excludes investments with a carrying value of $12 million and fair value of $35 million at September 30, 2017 , for which fair value is measured at net asset value (or its equivalent) as a practical expedient.

Offsetting Assets and Liabili54

Offsetting Assets and Liabilities Offsetting Assets and Liabilities (Assets) (Tables)	9 Months Ended
	Sep. 30, 2017
Offsetting Assets and Liabilities [Abstract]
Offsetting Assets and liabilities [Table Text Block]	The composition of offsetting derivative instruments, financial assets, and financial liabilities was as follows. Gross amounts of recognized assets/(liabilities) Gross amounts offset in the Condensed Consolidated Balance Sheet Net amounts of assets/(liabilities) presented in the Condensed Consolidated Balance Sheet Gross amounts not offset in the Condensed Consolidated Balance Sheet September 30, 2017 ($ in millions) Financial instruments Collateral (a) (b) (c) Net amount Assets Derivative assets in net asset positions $ 36 $ — $ 36 $ — $ (4 ) $ 32 Derivative assets in net liability positions — — — — — — Derivative assets with no offsetting arrangements 1 — 1 — — 1 Total assets (d) $ 37 $ — $ 37 $ — $ (4 ) $ 33 Liabilities Derivative liabilities in net liability positions $ (30 ) $ — $ (30 ) $ — $ — $ (30 ) Derivative liabilities in net asset positions — — — — — — Total derivative liabilities (d) (30 ) — (30 ) — — (30 ) Securities sold under agreements to repurchase (e) (1,171 ) — (1,171 ) — 1,171 — Total liabilities $ (1,201 ) $ — $ (1,201 ) $ — $ 1,171 $ (30 ) (a) Financial collateral received/pledged shown as a balance based on the sum of all net asset and liability positions between Ally and each individual derivative counterparty. (b) Amounts disclosed are limited to the financial asset or liability balance and, accordingly, exclude excess collateral received or pledged and noncash collateral received. $2 million of noncash derivative collateral pledged to us was excluded at September 30, 2017 . We do not record such collateral received on our Condensed Consolidated Balance Sheet unless certain conditions are met. (c) Certain agreements grant us the right to sell or pledge the noncash assets we receive as collateral. Noncash collateral pledged to us where the agreement grants us the right to sell or pledge the underlying assets had a fair value of $2 million at September 30, 2017 . We have not sold or pledged any of the noncash collateral received under these agreements as of September 30, 2017 . (d) For additional information on derivative instruments and hedging activities, refer to Note 19 . (e) For additional information on securities sold under agreements to repurchase, refer to Note 14 . Gross amounts of recognized assets/(liabilities) Gross amounts offset in the Condensed Consolidated Balance Sheet Net amounts of assets/(liabilities) presented in the Condensed Consolidated Balance Sheet Gross amounts not offset in the Condensed Consolidated Balance Sheet December 31, 2016 ($ in millions) Financial instruments Collateral (a) (b) (c) Net amount Assets Derivative assets in net asset positions $ 87 $ — $ 87 $ (4 ) $ (9 ) $ 74 Derivative assets in net liability positions 8 — 8 (8 ) — — Total assets (d) $ 95 $ — $ 95 $ (12 ) $ (9 ) $ 74 Liabilities Derivative liabilities in net liability positions $ (91 ) $ — $ (91 ) $ 8 $ 13 $ (70 ) Derivative liabilities in net asset positions (4 ) — (4 ) 4 — — Total derivative liabilities (d) (95 ) — (95 ) 12 13 (70 ) Securities sold under agreements to repurchase (e) (676 ) — (676 ) — 676 — Total liabilities $ (771 ) $ — $ (771 ) $ 12 $ 689 $ (70 ) (a) Financial collateral received/pledged shown as a balance based on the sum of all net asset and liability positions between Ally and each individual derivative counterparty. (b) Amounts disclosed are limited to the financial asset or liability balance and, accordingly, exclude excess collateral received or pledged and noncash collateral received. $6 million of noncash derivative collateral pledged to us was excluded at December 31, 2016. We do not record such collateral received on our Condensed Consolidated Balance Sheet unless certain conditions are met. (c) Certain agreements grant us the right to sell or pledge the noncash assets we receive as collateral. Noncash collateral pledged to us where the agreement grants us the right to sell or pledge the underlying assets had a fair value of $6 million at December 31, 2016. We have not sold or pledged any of the noncash collateral received under these agreements as of December 31, 2016. (d) For additional information on derivative instruments and hedging activities, refer to Note 19 . (e) For additional information on securities sold under agreements to repurchase, refer to Note 14 .

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment [Table Text Block]	Financial information for our reportable operating segments is summarized as follows. Three months ended September 30, ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated (a) 2017 Net financing revenue and other interest income $ 950 $ 15 $ 32 $ 39 $ 45 $ 1,081 Other revenue 82 272 2 5 20 381 Total net revenue 1,032 287 34 44 65 1,462 Provision for loan losses 312 — 4 3 (5 ) 314 Total noninterest expense 420 218 28 19 68 753 Income from continuing operations before income tax expense $ 300 $ 69 $ 2 $ 22 $ 2 $ 395 Total assets $ 112,141 $ 7,432 $ 9,804 $ 3,699 $ 30,937 $ 164,013 2016 Net financing revenue and other interest income (loss) $ 933 $ 14 $ 25 $ 30 $ (6 ) $ 996 Other revenue 74 264 — 4 46 388 Total net revenue 1,007 278 25 34 40 1,384 Provision for loan losses 270 — 1 3 (16 ) 258 Total noninterest expense 418 222 16 16 63 735 Income (loss) from continuing operations before income tax expense $ 319 $ 56 $ 8 $ 15 $ (7 ) $ 391 Total assets $ 113,669 $ 7,259 $ 7,933 $ 3,232 $ 25,304 $ 157,397 (a) Net financing revenue and other interest income after the provision for loan losses totaled $767 million and $738 million for the three months ended September 30, 2017 , and 2016 , respectively. Nine months ended September 30, ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated (a) 2017 Net financing revenue and other interest income $ 2,774 $ 44 $ 98 $ 121 $ 90 $ 3,127 Other revenue 290 781 3 33 58 1,165 Total net revenue 3,064 825 101 154 148 4,292 Provision for loan losses 846 — 6 15 (13 ) 854 Total noninterest expense 1,283 737 77 57 187 2,341 Income (loss) from continuing operations before income tax expense $ 935 $ 88 $ 18 $ 82 $ (26 ) $ 1,097 Total assets $ 112,141 $ 7,432 $ 9,804 $ 3,699 $ 30,937 $ 164,013 2016 Net financing revenue and other interest income (loss) $ 2,758 $ 44 $ 71 $ 87 $ (29 ) $ 2,931 Other revenue 228 777 — 14 119 1,138 Total net revenue 2,986 821 71 101 90 4,069 Provision for loan losses 649 — 4 12 (15 ) 650 Total noninterest expense 1,255 733 48 49 133 2,218 Income (loss) from continuing operations before income tax expense $ 1,082 $ 88 $ 19 $ 40 $ (28 ) $ 1,201 Total assets $ 113,669 $ 7,259 $ 7,933 $ 3,232 $ 25,304 $ 157,397 (a) Net financing revenue and other interest income after the provision for loan losses totaled $2,273 million and $2,281 million for the nine months ended September 30, 2017 , and 2016 , respectively.

Parent and Guarantor Condense56

Parent and Guarantor Condensed Consolidating Financial Statements (Tables)	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Condensed Income Statement [Table Text Block]	Condensed Consolidating Statements of Comprehensive Income Three months ended September 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing revenue and other interest income Interest and fees on finance receivables and loans $ 13 $ — $ 1,473 $ — $ 1,486 Interest and fees on finance receivables and loans — intercompany 2 — 1 (3 ) — Interest and dividends on investment securities and other earning assets — — 157 — 157 Interest on cash and cash equivalents 2 — 9 — 11 Interest-bearing cash — intercompany 1 — 2 (3 ) — Operating leases 3 — 431 — 434 Total financing revenue and other interest income 21 — 2,073 (6 ) 2,088 Interest expense Interest on deposits — — 286 (1 ) 285 Interest on short-term borrowings 16 — 18 — 34 Interest on long-term debt 278 — 138 — 416 Interest on intercompany debt 3 — 2 (5 ) — Total interest expense 297 — 444 (6 ) 735 Net depreciation expense on operating lease assets 3 — 269 — 272 Net financing revenue (279 ) — 1,360 — 1,081 Cash dividends from subsidiaries Bank subsidiary 2,900 2,900 — (5,800 ) — Nonbank subsidiaries 101 — — (101 ) — Other revenue Insurance premiums and service revenue earned — — 252 — 252 Gain on mortgage and automotive loans, net 9 — 6 — 15 Loss on extinguishment of debt (1 ) — (3 ) — (4 ) Other gain on investments, net — — 23 — 23 Other income, net of losses 138 — 199 (242 ) 95 Total other revenue 146 — 477 (242 ) 381 Total net revenue 2,868 2,900 1,837 (6,143 ) 1,462 Provision for loan losses 161 — 153 — 314 Noninterest expense Compensation and benefits expense 17 — 247 — 264 Insurance losses and loss adjustment expenses — — 65 — 65 Other operating expenses 208 — 459 (243 ) 424 Total noninterest expense 225 — 771 (243 ) 753 Income from continuing operations before income tax (benefit) expense and undistributed (loss) income of subsidiaries 2,482 2,900 913 (5,900 ) 395 Income tax (benefit) expense from continuing operations (135 ) — 250 — 115 Net income from continuing operations 2,617 2,900 663 (5,900 ) 280 Income (loss) from discontinued operations, net of tax 4 — (2 ) — 2 Undistributed (loss) income of subsidiaries Bank subsidiary (2,524 ) (2,524 ) — 5,048 — Nonbank subsidiaries 185 — — (185 ) — Net income 282 376 661 (1,037 ) 282 Other comprehensive income, net of tax 48 36 51 (87 ) 48 Comprehensive income $ 330 $ 412 $ 712 $ (1,124 ) $ 330 Three months ended September 30, 2016 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing (loss) revenue and other interest income Interest and fees on finance receivables and loans $ (15 ) $ — $ 1,322 $ — $ 1,307 Interest and fees on finance receivables and loans — intercompany 2 — 2 (4 ) — Interest and dividends on investment securities and other earning assets — — 102 (1 ) 101 Interest on cash and cash equivalents 1 — 2 — 3 Interest-bearing cash — intercompany — — 2 (2 ) — Operating leases 4 — 645 — 649 Total financing (loss) revenue and other interest income (8 ) — 2,075 (7 ) 2,060 Interest expense Interest on deposits 2 — 210 — 212 Interest on short-term borrowings 10 — 4 — 14 Interest on long-term debt 289 — 141 — 430 Interest on intercompany debt 5 — 2 (7 ) — Total interest expense 306 — 357 (7 ) 656 Net depreciation expense on operating lease assets 3 — 405 — 408 Net financing revenue (317 ) — 1,313 — 996 Cash dividends from subsidiaries Nonbank subsidiaries 170 — — (170 ) — Other revenue Insurance premiums and service revenue earned — — 238 — 238 (Loss) gain on mortgage and automotive loans, net (7 ) — 7 — — Other gain on investments, net — — 52 — 52 Other income, net of losses 298 — 231 (431 ) 98 Total other revenue 291 — 528 (431 ) 388 Total net revenue 144 — 1,841 (601 ) 1,384 Provision for loan losses 147 — 111 — 258 Noninterest expense Compensation and benefits expense 143 — 105 — 248 Insurance losses and loss adjustment expenses — — 69 — 69 Other operating expenses 307 — 541 (430 ) 418 Total noninterest expense 450 — 715 (430 ) 735 (Loss) income from continuing operations before income tax (benefit) expense and undistributed income of subsidiaries (453 ) — 1,015 (171 ) 391 Income tax (benefit) expense from continuing operations (88 ) — 218 — 130 Net (loss) income from continuing operations (365 ) — 797 (171 ) 261 Loss from discontinued operations, net of tax (47 ) — (5 ) — (52 ) Undistributed income of subsidiaries Bank subsidiary 325 325 — (650 ) — Nonbank subsidiaries 296 — — (296 ) — Net income 209 325 792 (1,117 ) 209 Other comprehensive loss, net of tax (4 ) (3 ) (9 ) 12 (4 ) Comprehensive income $ 205 $ 322 $ 783 $ (1,105 ) $ 205 Nine months ended September 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing (loss) revenue and other interest income Interest and fees on finance receivables and loans $ (57 ) $ — $ 4,358 $ — $ 4,301 Interest and fees on finance receivables and loans — intercompany 10 — 5 (15 ) — Interest and dividends on investment securities and other earning assets — — 439 (2 ) 437 Interest on cash and cash equivalents 6 — 17 — 23 Interest-bearing cash — intercompany 1 — 5 (6 ) — Operating leases 9 — 1,456 — 1,465 Total financing (loss) revenue and other interest income (31 ) — 6,280 (23 ) 6,226 Interest expense Interest on deposits 2 — 765 (1 ) 766 Interest on short-term borrowings 52 — 42 — 94 Interest on long-term debt 834 — 423 — 1,257 Interest on intercompany debt 12 — 10 (22 ) — Total interest expense 900 — 1,240 (23 ) 2,117 Net depreciation expense on operating lease assets 8 — 974 — 982 Net financing revenue (939 ) — 4,066 — 3,127 Cash dividends from subsidiaries Bank subsidiary 2,900 2,900 — (5,800 ) — Nonbank subsidiaries 528 — — (528 ) — Other revenue Insurance premiums and service revenue earned — — 720 — 720 Gain on mortgage and automotive loans, net 39 — 26 — 65 Loss on extinguishment of debt (1 ) — (5 ) — (6 ) Other gain on investments, net — — 73 — 73 Other income, net of losses 569 — 635 (891 ) 313 Total other revenue 607 — 1,449 (891 ) 1,165 Total net revenue 3,096 2,900 5,515 (7,219 ) 4,292 Provision for loan losses 350 — 504 — 854 Noninterest expense Compensation and benefits expense 157 — 657 — 814 Insurance losses and loss adjustment expenses — — 278 — 278 Other operating expenses 709 — 1,431 (891 ) 1,249 Total noninterest expense 866 — 2,366 (891 ) 2,341 Income from continuing operations before income tax (benefit) expense and undistributed (loss) income of subsidiaries 1,880 2,900 2,645 (6,328 ) 1,097 Income tax (benefit) expense from continuing operations (362 ) — 712 — 350 Net income from continuing operations 2,242 2,900 1,933 (6,328 ) 747 Income (loss) from discontinued operations, net of tax 6 — (5 ) — 1 Undistributed (loss) income of subsidiaries Bank subsidiary (1,760 ) (1,760 ) — 3,520 — Nonbank subsidiaries 260 — — (260 ) — Net income 748 1,140 1,928 (3,068 ) 748 Other comprehensive income, net of tax 144 91 140 (231 ) 144 Comprehensive income $ 892 $ 1,231 $ 2,068 $ (3,299 ) $ 892 Nine months ended September 30, 2016 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing (loss) revenue and other interest income Interest and fees on finance receivables and loans $ (82 ) $ — $ 3,889 $ — $ 3,807 Interest and fees on finance receivables and loans — intercompany 8 — 6 (14 ) — Interest and dividends on investment securities and other earning assets — — 303 (1 ) 302 Interest on cash and cash equivalents 4 — 6 — 10 Interest-bearing cash — intercompany — — 7 (7 ) — Operating leases 14 — 2,105 — 2,119 Total financing (loss) revenue and other interest income (56 ) — 6,316 (22 ) 6,238 Interest expense Interest on deposits 6 — 602 — 608 Interest on short-term borrowings 31 — 8 — 39 Interest on long-term debt 868 — 440 — 1,308 Interest on intercompany debt 14 — 8 (22 ) — Total interest expense 919 — 1,058 (22 ) 1,955 Net depreciation expense on operating lease assets 11 — 1,341 — 1,352 Net financing revenue (986 ) — 3,917 — 2,931 Cash dividends from subsidiaries Nonbank subsidiaries 800 — — (800 ) — Other revenue Insurance premiums and service revenue earned — — 704 — 704 (Loss) gain on mortgage and automotive loans, net (11 ) — 15 — 4 Loss on extinguishment of debt (2 ) — (2 ) — (4 ) Other gain on investments, net — — 145 — 145 Other income, net of losses 989 — 661 (1,361 ) 289 Total other revenue 976 — 1,523 (1,361 ) 1,138 Total net revenue 790 — 5,440 (2,161 ) 4,069 Provision for loan losses 295 — 355 — 650 Noninterest expense Compensation and benefits expense 430 — 312 — 742 Insurance losses and loss adjustment expenses — — 287 — 287 Other operating expenses 963 — 1,586 (1,360 ) 1,189 Total noninterest expense 1,393 — 2,185 (1,360 ) 2,218 (Loss) income from continuing operations before income tax (benefit) expense and undistributed income (loss) of subsidiaries (898 ) — 2,900 (801 ) 1,201 Income tax (benefit) expense from continuing operations (196 ) (82 ) 614 — 336 Net (loss) income from continuing operations (702 ) 82 2,286 (801 ) 865 Loss from discontinued operations, net of tax (39 ) — (7 ) — (46 ) Undistributed income (loss) of subsidiaries Bank subsidiary 932 932 — (1,864 ) — Nonbank subsidiaries 628 (2 ) — (626 ) — Net income 819 1,012 2,279 (3,291 ) 819 Other comprehensive income, net of tax 262 143 234 (377 ) 262 Comprehensive income $ 1,081 $ 1,155 $ 2,513 $ (3,668 ) $ 1,081
Condensed Balance Sheet [Table Text Block]	Condensed Consolidating Balance Sheet September 30, 2017 ($ in millions) Parent (a) Guarantors Nonguarantors (a) Consolidating adjustments Ally consolidated Assets Cash and cash equivalents Noninterest-bearing $ 74 $ — $ 736 $ — $ 810 Interest-bearing 5 — 3,609 — 3,614 Interest-bearing — intercompany 1,495 — 558 (2,053 ) — Total cash and cash equivalents 1,574 — 4,903 (2,053 ) 4,424 Available-for-sale securities — — 23,099 — 23,099 Held-to-maturity securities — — 1,923 (84 ) 1,839 Loans held-for-sale, net — — 18 — 18 Finance receivables and loans, net Finance receivables and loans, net 7,694 — 111,177 — 118,871 Intercompany loans to Nonbank subsidiaries 788 — 394 (1,182 ) — Allowance for loan losses (197 ) — (1,089 ) — (1,286 ) Total finance receivables and loans, net 8,285 — 110,482 (1,182 ) 117,585 Investment in operating leases, net 23 — 8,908 — 8,931 Intercompany receivables from Bank subsidiary 59 — — (59 ) — Nonbank subsidiaries 76 — 91 (167 ) — Investment in subsidiaries Bank subsidiary 16,383 16,383 — (32,766 ) — Nonbank subsidiaries 9,045 — — (9,045 ) — Premiums receivable and other insurance assets — — 2,085 (31 ) 2,054 Other assets 3,174 — 4,910 (2,021 ) 6,063 Total assets $ 38,619 $ 16,383 $ 156,419 $ (47,408 ) $ 164,013 Liabilities Deposit liabilities Noninterest-bearing $ — $ — $ 129 $ — $ 129 Interest-bearing 14 — 89,973 — 89,987 Interest-bearing — intercompany — — 1,495 (1,495 ) — Total deposit liabilities 14 — 91,597 (1,495 ) 90,116 Short-term borrowings 3,379 — 6,796 — 10,175 Long-term debt 19,969 — 25,153 — 45,122 Intercompany debt to Bank subsidiary 84 — — (84 ) — Nonbank subsidiaries 952 — 788 (1,740 ) — Intercompany payables to Nonbank subsidiaries 149 — 108 (257 ) — Interest payable 278 — 274 — 552 Unearned insurance premiums and service revenue — — 2,583 — 2,583 Accrued expenses and other liabilities 221 — 3,692 (2,021 ) 1,892 Total liabilities 25,046 — 130,991 (5,597 ) 150,440 Total equity 13,573 16,383 25,428 (41,811 ) 13,573 Total liabilities and equity $ 38,619 $ 16,383 $ 156,419 $ (47,408 ) $ 164,013 (a) Amounts presented are based upon the legal transfer of the underlying assets to VIEs in order to reflect legal ownership. December 31, 2016 ($ in millions) Parent (a) Guarantors Nonguarantors (a) Consolidating adjustments Ally consolidated Assets Cash and cash equivalents Noninterest-bearing $ 720 $ — $ 827 $ — $ 1,547 Interest-bearing 100 — 4,287 — 4,387 Interest-bearing — intercompany — — 401 (401 ) — Total cash and cash equivalents 820 — 5,515 (401 ) 5,934 Trading securities — — 82 (82 ) — Available-for-sale securities — — 19,253 (327 ) 18,926 Held-to-maturity securities — — 839 — 839 Finance receivables and loans, net Finance receivables and loans, net 4,705 — 114,239 — 118,944 Intercompany loans to Bank subsidiary 1,125 — — (1,125 ) — Nonbank subsidiaries 1,779 — 626 (2,405 ) — Allowance for loan losses (115 ) — (1,029 ) — (1,144 ) Total finance receivables and loans, net 7,494 — 113,836 (3,530 ) 117,800 Investment in operating leases, net 42 — 11,428 — 11,470 Intercompany receivables from Bank subsidiary 299 — — (299 ) — Nonbank subsidiaries 107 — 67 (174 ) — Investment in subsidiaries Bank subsidiary 17,727 17,727 — (35,454 ) — Nonbank subsidiaries 10,318 — — (10,318 ) — Premiums receivable and other insurance assets — — 1,936 (31 ) 1,905 Other assets 4,347 — 5,085 (2,578 ) 6,854 Total assets $ 41,154 $ 17,727 $ 158,041 $ (53,194 ) $ 163,728 Liabilities Deposit liabilities Noninterest-bearing $ — $ — $ 84 $ — $ 84 Interest-bearing 167 — 78,771 — 78,938 Total deposit liabilities 167 — 78,855 — 79,022 Short-term borrowings 3,622 — 9,051 — 12,673 Long-term debt 21,798 — 32,330 — 54,128 Intercompany debt to Bank subsidiary 330 — — (330 ) — Nonbank subsidiaries 1,027 — 2,903 (3,930 ) — Intercompany payables to Nonbank subsidiaries 153 — 351 (504 ) — Interest payable 253 — 98 — 351 Unearned insurance premiums and service revenue — — 2,500 — 2,500 Accrued expenses and other liabilities 487 — 3,911 (2,661 ) 1,737 Total liabilities 27,837 — 129,999 (7,425 ) 150,411 Total equity 13,317 17,727 28,042 (45,769 ) 13,317 Total liabilities and equity $ 41,154 $ 17,727 $ 158,041 $ (53,194 ) $ 163,728 (a) Amounts presented are based upon the legal transfer of the underlying assets to VIEs in order to reflect legal ownership.
Condensed Cash Flow Statement [Table Text Block]	Condensed Consolidating Statement of Cash Flows Nine months ended September 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Operating activities Net cash provided by operating activities $ 3,701 $ 2,900 $ 3,019 $ (6,247 ) $ 3,373 Investing activities Purchases of available-for-sale securities — — (9,022 ) — (9,022 ) Proceeds from sales of available-for-sale securities — — 2,926 — 2,926 Proceeds from maturities and repayments of available-for-sale securities — — 2,002 — 2,002 Purchases of held-to-maturity securities — — (709 ) — (709 ) Proceeds from maturities and repayments of held-to-maturity securities — — 32 — 32 Net change in investment securities — intercompany 7 — 281 (288 ) — Purchases of finance receivables and loans held-for-investment (35 ) — (3,090 ) — (3,125 ) Proceeds from sales of finance receivables and loans originated as held-for-investment 96 — 1,227 — 1,323 Originations and repayments of finance receivables and loans held-for-investment and other, net 259 — 2,718 (1,956 ) 1,021 Net change in loans — intercompany 2,159 — 232 (2,391 ) — Purchases of operating lease assets — — (2,844 ) — (2,844 ) Disposals of operating lease assets 7 — 4,402 — 4,409 Capital contributions to subsidiaries (1,200 ) — — 1,200 — Returns of contributed capital 1,031 — — (1,031 ) — Net change in restricted cash (19 ) — 521 (5 ) 497 Net change in nonmarketable equity investments — — (20 ) — (20 ) Other, net (25 ) — (43 ) (91 ) (159 ) Net cash provided by (used in) investing activities 2,280 — (1,387 ) (4,562 ) (3,669 ) Financing activities Net change in short-term borrowings — third party (245 ) — (2,255 ) — (2,500 ) Net (decrease) increase in deposits (153 ) — 12,698 (1,495 ) 11,050 Proceeds from issuance of long-term debt — third party 355 — 10,986 1,961 13,302 Repayments of long-term debt — third party (4,125 ) — (18,251 ) — (22,376 ) Net change in debt — intercompany (366 ) — (2,166 ) 2,532 — Repurchase of common stock (563 ) — — — (563 ) Dividends paid — third party (130 ) — — — (130 ) Dividends paid and returns of contributed capital — intercompany — (2,900 ) (4,459 ) 7,359 — Capital contributions from parent — — 1,200 (1,200 ) — Net cash used in financing activities (5,227 ) (2,900 ) (2,247 ) 9,157 (1,217 ) Effect of exchange-rate changes on cash and cash equivalents — — 3 — 3 Net increase (decrease) in cash and cash equivalents 754 — (612 ) (1,652 ) (1,510 ) Cash and cash equivalents at beginning of year 820 — 5,515 (401 ) 5,934 Cash and cash equivalents at September 30, $ 1,574 $ — $ 4,903 $ (2,053 ) $ 4,424 Nine months ended September 30, 2016 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Operating activities Net cash provided by operating activities $ 709 $ — $ 3,782 $ (902 ) $ 3,589 Investing activities Purchases of available-for-sale securities — — (11,027 ) — (11,027 ) Proceeds from sales of available-for-sale securities — — 8,546 — 8,546 Proceeds from maturities and repayments of available-for-sale securities — — 2,411 — 2,411 Purchases of held-to-maturity securities — — (650 ) — (650 ) Purchases of finance receivables and loans held-for-investment — — (2,924 ) — (2,924 ) Proceeds from sales of finance receivables and loans originated as held-for-investment — — 4,221 — 4,221 Originations and repayments of finance receivables and loans held-for-investment and other, net 934 — (6,318 ) — (5,384 ) Net change in loans — intercompany 1,788 — (41 ) (1,747 ) — Purchases of operating lease assets — — (2,360 ) — (2,360 ) Disposals of operating lease assets 16 — 4,615 — 4,631 Acquisitions, net of cash acquired (309 ) — — — (309 ) Capital contributions to subsidiaries (3,112 ) — — 3,112 — Returns of contributed capital 2,168 8 — (2,176 ) — Net change in restricted cash (136 ) — 758 622 Net change in nonmarketable equity investments — — (401 ) — (401 ) Other, net (156 ) — (103 ) 102 (157 ) Net cash provided by (used in) investing activities 1,193 8 (3,273 ) (709 ) (2,781 ) Financing activities Net change in short-term borrowings — third party 72 — (1,745 ) — (1,673 ) Net (decrease) increase in deposits (36 ) — 9,276 — 9,240 Proceeds from issuance of long-term debt — third party 1,084 — 10,145 — 11,229 Repayments of long-term debt — third party (2,279 ) — (18,479 ) — (20,758 ) Net change in debt — intercompany (30 ) — (1,788 ) 1,818 — Redemption of preferred stock (696 ) — — — (696 ) Repurchase of common stock (173 ) — — — (173 ) Dividends paid — third party (70 ) — — — (70 ) Dividends paid and returns of contributed capital — intercompany — (8 ) (2,968 ) 2,976 — Capital contributions from parent — — 3,112 (3,112 ) — Net cash used in financing activities (2,128 ) (8 ) (2,447 ) 1,682 (2,901 ) Effect of exchange-rate changes on cash and cash equivalents — — 2 — 2 Net decrease in cash and cash equivalents (226 ) — (1,936 ) 71 (2,091 ) Cash and cash equivalents at beginning of year 1,635 — 5,595 (850 ) 6,380 Cash and cash equivalents at September 30, $ 1,409 $ — $ 3,659 $ (779 ) $ 4,289

Acquisitions Acquisitions (Deta

Acquisitions Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Aug. 01, 2016	Jun. 01, 2016
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross						$ 28	$ 298
Goodwill	$ 240		$ 240		$ 240
Amortization of Intangible Assets	3	$ 3	8	$ 3
Other Intangible Assets [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill							82
Cash and Cash Equivalents [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents							50
Other Assets [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill							14
Deferred Tax Asset [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill							4
Employee compensation and benefits [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents							40
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities							(41)
Other Liabilities [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities							(4)
Corporate and Other [Member]
Business Acquisition [Line Items]
Goodwill	193		193		193		$ 193
Automotive Finance Operations [Member]
Business Acquisition [Line Items]
Goodwill	$ 20		$ 20		$ 20	$ 20

Discontinued Operations (Detail

Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Discontinued Operations and Disposal Groups [Abstract]
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	$ (1)	$ (46)	$ (2)	$ (44)
Discontinued Operation, Tax Effect of Discontinued Operation	$ (3)	$ 6	$ (3)	$ 2

Other Income, Net of Losses (Sc

Other Income, Net of Losses (Schedule of Other Income, Net of Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Nonoperating Income (Expense) [Abstract]
Remarketing Fees	$ 26	$ 26	$ 82	$ 79
Fees and Commissions, Other	25	25	77	72
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	11	18	41	49
Income (Loss) from Equity Method Investments	7	3	12	14
Other Income	26	26	101	75
Noninterest Income, Other Operating Income	$ 95	$ 98	$ 313	$ 289

Reserves for Insurance Losses60

Reserves for Insurance Losses and Loss Adjustment Expenses Reserves for Insurance Losses and Loss Adjustment Expenses (Schedule of Liability for Unpaid Claims and Claims Adjustment Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Liability for Claims and Claims Adjustment Expenses (Rollforward) [Abstract]
Liability for Claims and Claims Adjustment Expense			$ 149	$ 169
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments			108	120
Liability for Unpaid Claims and Claims Adjustment Expense, Net			41	49
Current Year Claims and Claims Adjustment Expense			276	291
Prior Year Claims and Claims Adjustment Expense			2	(4)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	$ 65	$ 69	278	287
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year			(248)	(266)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years			(31)	(27)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid			(279)	(293)
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)			1	1
Liability for Unpaid Claims and Claims Adjustment Expense, Net	41	44	41	44
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	132	106	132	106
Liability for Claims and Claims Adjustment Expense	$ 173	$ 150	$ 173	$ 150

Other Operating Expenses (Sched

Other Operating Expenses (Schedule Of Other Operating Expenses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating Expenses [Abstract]
Insurance Commissions	$ 106	$ 99	$ 309	$ 290
Communications and Information Technology	72	70	212	203
Lease And Loan Administration	41	34	116	100
Marketing and Advertising Expense	33	27	96	75
Vehicle remarketing and repossession	29	24	82	70
Federal Deposit Insurance Corporation Premium Expense	27	26	82	68
Professional Fees	28	25	81	75
Depreciation, Nonproduction	22	19	67	61
Occupancy, Net	11	13	34	38
Taxes, Miscellaneous	6	10	22	27
Other Cost and Expense, Operating	49	71	148	182
Other Noninterest Expense	$ 424	$ 418	$ 1,249	$ 1,189

Investment Securities (Investme

Investment Securities (Investment Table) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment		$ 839
Available-for-sale Securities, Amortized Cost Basis	$ 23,266	19,293
Available-for-sale Securities, Gross Unrealized Gains	112	68
Available-for-sale Securities, Gross Unrealized Losses	(279)	(435)
Available-for-sale securities	23,099	18,926
Held-to-maturity securities	1,839	839
Held-to-maturity Securities, Fair Value	1,807	789
Fair Value Hedge Assets	304
Deposit Assets	12	14
Pledged Assets Separately Reported, Securities Pledged for Federal Home Loan Bank, at Fair Value	6,705	4,881
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	1,339	737
Cash Equivalents, at Carrying Value	304	$ 291
Held-to-Maturity Debt Securities, Yield		2.90%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount		$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield		0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount		$ 0
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield		0.00%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount		$ 0
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield		0.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount		$ 839
Held-to-Maturity Securities, Due After Ten Years, Yield		2.90%
Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	22,703	$ 18,651
Available-for-sale Debt Securities Gross Unrealized Gain	100	61
Available-for-sale Debt Securities, Gross Unrealized Loss	(229)	(381)
Available-for-sale Securities, Debt Securities	22,574	18,331
US Treasury and Government [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,112	1,680
Available-for-sale Debt Securities Gross Unrealized Gain	0	0
Available-for-sale Debt Securities, Gross Unrealized Loss	(39)	(60)
Available-for-sale Securities, Debt Securities	2,073	1,620
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	849	794
Available-for-sale Debt Securities Gross Unrealized Gain	12	7
Available-for-sale Debt Securities, Gross Unrealized Loss	(10)	(19)
Available-for-sale Securities, Debt Securities	851	782
Foreign Government Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	157	157
Available-for-sale Debt Securities Gross Unrealized Gain	2	5
Available-for-sale Debt Securities, Gross Unrealized Loss	(2)	0
Available-for-sale Securities, Debt Securities	157	162
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	14,423	10,473
Available-for-sale Debt Securities Gross Unrealized Gain	54	29
Available-for-sale Debt Securities, Gross Unrealized Loss	(133)	(212)
Available-for-sale Securities, Debt Securities	14,344	10,290
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,799
Held-to-maturity securities	1,799	839
Held-to-maturity Securities, Unrecognized Holding Gain	4	0
Held-to-maturity Securities, Unrecognized Holding Loss	(36)	(50)
Held-to-maturity Securities, Fair Value	$ 1,767	789
Held-to-Maturity Debt Securities, Yield	3.10%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 1,799
Held-to-Maturity Securities, Due After Ten Years, Yield	3.10%
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 2,326	2,162
Available-for-sale Debt Securities Gross Unrealized Gain	16	5
Available-for-sale Debt Securities, Gross Unrealized Loss	(32)	(70)
Available-for-sale Securities, Debt Securities	2,310	2,097
Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	509	537
Available-for-sale Debt Securities Gross Unrealized Gain	2	2
Available-for-sale Debt Securities, Gross Unrealized Loss	(2)	(2)
Available-for-sale Securities, Debt Securities	509	537
Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,036	1,396
Available-for-sale Debt Securities Gross Unrealized Gain	4	6
Available-for-sale Debt Securities, Gross Unrealized Loss	(1)	(2)
Available-for-sale Securities, Debt Securities	1,039	1,400
Asset-backed Securities [Member] | Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	40
Held-to-maturity securities	40	0
Held-to-maturity Securities, Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Unrecognized Holding Loss	0	0
Held-to-maturity Securities, Fair Value	$ 40	0
Held-to-Maturity Debt Securities, Yield	1.70%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 39
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield	1.60%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 1
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield	3.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 0
Held-to-Maturity Securities, Due After Ten Years, Yield	0.00%
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 1,291	1,452
Available-for-sale Debt Securities Gross Unrealized Gain	10	7
Available-for-sale Debt Securities, Gross Unrealized Loss	(10)	(16)
Available-for-sale Securities, Debt Securities	1,291	1,443
Equity Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	563	642
Available-for-sale Equity Securities, Gross Unrealized Gain	12	7
Available-for-sale Equity Securities, Gross Unrealized Loss	(50)	(54)
Available-for-sale Securities, Equity Securities	525	595
Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,839
Held-to-maturity securities	1,839	839
Held-to-maturity Securities, Unrecognized Holding Gain	4	0
Held-to-maturity Securities, Unrecognized Holding Loss	(36)	(50)
Held-to-maturity Securities, Fair Value	$ 1,807	789
Held-to-Maturity Debt Securities, Yield	3.10%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 39
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield	1.60%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 1
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield	3.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 1,799
Held-to-Maturity Securities, Due After Ten Years, Yield	3.10%
Federal Home Loan Bank Certificates and Obligations (FHLB) [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Fair Value	$ 115	$ 87

Investment Securities (Invest63

Investment Securities (Investments Classified by Contractual Maturity Date) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment		$ 839
Held-to-Maturity Debt Securities, Yield		2.90%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount		$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield		0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount		$ 0
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield		0.00%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount		$ 0
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield		0.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount		$ 839
Held-to-Maturity Securities, Due After Ten Years, Yield		2.90%
Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 22,574	$ 18,331
Available-for-sale debt securities, Yield	2.90%	2.80%
Available-for-sale debt securities, Due in one year or less, Amount	$ 206	$ 138
Available-for-sale debt securities, Due in one year or less, Yield	2.20%	2.00%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 1,928	$ 2,046
Available-for-sale debt securities, Due after one year through five years, Yield	2.60%	2.70%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 2,577	$ 2,498
Available-for-sale debt securities, Due after five years through ten years, Yield	2.20%	2.20%
Available-for-sale debt securities, Due after ten years, Amount	$ 17,863	$ 13,649
Available-for-sale debt securities, Due after ten years, Yield	3.10%	2.90%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 22,703	$ 18,651
Amortized cost of available-for-sale debt securities, Due in one year or less, Amount	206	138
Amortized cost of available-for-sale debt securities, Due after one year through five years, Amount	1,929	2,040
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	2,609	2,563
Amortized cost of available-for-sale debt securities, Due after ten years, Amount	17,959	13,910
US Treasury and Government [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 2,073	$ 1,620
Available-for-sale debt securities, Yield	1.80%	1.70%
Available-for-sale debt securities, Due in one year or less, Amount	$ 0	$ 2
Available-for-sale debt securities, Due in one year or less, Yield	0.00%	4.60%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 467	$ 60
Available-for-sale debt securities, Due after one year through five years, Yield	1.70%	1.60%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 1,606	$ 1,558
Available-for-sale debt securities, Due after five years through ten years, Yield	1.80%	1.70%
Available-for-sale debt securities, Due after ten years, Amount	$ 0	$ 0
Available-for-sale debt securities, Due after ten years, Yield	0.00%	0.00%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 2,112	$ 1,680
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 851	$ 782
Available-for-sale debt securities, Yield	2.90%	3.10%
Available-for-sale debt securities, Due in one year or less, Amount	$ 69	$ 64
Available-for-sale debt securities, Due in one year or less, Yield	1.60%	1.70%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 35	$ 29
Available-for-sale debt securities, Due after one year through five years, Yield	2.40%	2.30%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 197	$ 172
Available-for-sale debt securities, Due after five years through ten years, Yield	2.70%	2.80%
Available-for-sale debt securities, Due after ten years, Amount	$ 550	$ 517
Available-for-sale debt securities, Due after ten years, Yield	3.20%	3.40%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 849	$ 794
Foreign Government Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 157	$ 162
Available-for-sale debt securities, Yield	2.50%	2.60%
Available-for-sale debt securities, Due in one year or less, Amount	$ 0	$ 0
Available-for-sale debt securities, Due in one year or less, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 69	$ 58
Available-for-sale debt securities, Due after one year through five years, Yield	2.60%	2.80%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 88	$ 104
Available-for-sale debt securities, Due after five years through ten years, Yield	2.40%	2.40%
Available-for-sale debt securities, Due after ten years, Amount	$ 0	$ 0
Available-for-sale debt securities, Due after ten years, Yield	0.00%	0.00%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 157	$ 157
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 14,344	$ 10,290
Available-for-sale debt securities, Yield	3.10%	2.90%
Available-for-sale debt securities, Due in one year or less, Amount	$ 0	$ 0
Available-for-sale debt securities, Due in one year or less, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 0	$ 0
Available-for-sale debt securities, Due after one year through five years, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 3	$ 29
Available-for-sale debt securities, Due after five years through ten years, Yield	2.90%	2.60%
Available-for-sale debt securities, Due after ten years, Amount	$ 14,341	$ 10,261
Available-for-sale debt securities, Due after ten years, Yield	3.10%	2.90%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 14,423	$ 10,473
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 2,310	$ 2,097
Available-for-sale debt securities, Yield	3.00%	2.90%
Available-for-sale debt securities, Due in one year or less, Amount	$ 0	$ 0
Available-for-sale debt securities, Due in one year or less, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 0	$ 0
Available-for-sale debt securities, Due after one year through five years, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 0	$ 0
Available-for-sale debt securities, Due after five years through ten years, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after ten years, Amount	$ 2,310	$ 2,097
Available-for-sale debt securities, Due after ten years, Yield	3.00%	2.90%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 2,326	$ 2,162
Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 509	$ 537
Available-for-sale debt securities, Yield	3.10%	2.60%
Available-for-sale debt securities, Due in one year or less, Amount	$ 0	$ 0
Available-for-sale debt securities, Due in one year or less, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 0	$ 0
Available-for-sale debt securities, Due after one year through five years, Yield	0.00%	0.00%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 31	$ 3
Available-for-sale debt securities, Due after five years through ten years, Yield	2.90%	2.80%
Available-for-sale debt securities, Due after ten years, Amount	$ 478	$ 534
Available-for-sale debt securities, Due after ten years, Yield	3.10%	2.60%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 509	$ 537
Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 1,039	$ 1,400
Available-for-sale debt securities, Yield	3.00%	2.80%
Available-for-sale debt securities, Due in one year or less, Amount	$ 2	$ 0
Available-for-sale debt securities, Due in one year or less, Yield	1.60%	0.00%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 762	$ 1,059
Available-for-sale debt securities, Due after one year through five years, Yield	3.10%	2.80%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 137	$ 143
Available-for-sale debt securities, Due after five years through ten years, Yield	3.10%	3.20%
Available-for-sale debt securities, Due after ten years, Amount	$ 138	$ 198
Available-for-sale debt securities, Due after ten years, Yield	2.70%	2.60%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 1,036	$ 1,396
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 1,291	$ 1,443
Available-for-sale debt securities, Yield	2.90%	2.80%
Available-for-sale debt securities, Due in one year or less, Amount	$ 135	$ 72
Available-for-sale debt securities, Due in one year or less, Yield	2.50%	2.20%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 595	$ 840
Available-for-sale debt securities, Due after one year through five years, Yield	2.60%	2.60%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 515	$ 489
Available-for-sale debt securities, Due after five years through ten years, Yield	3.20%	3.20%
Available-for-sale debt securities, Due after ten years, Amount	$ 46	$ 42
Available-for-sale debt securities, Due after ten years, Yield	4.90%	4.70%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 1,291	$ 1,452
Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	$ 1,839
Held-to-Maturity Debt Securities, Yield	3.10%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 39
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield	1.60%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 1
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield	3.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 1,799
Held-to-Maturity Securities, Due After Ten Years, Yield	3.10%
Held-to-maturity Securities [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	$ 1,799
Held-to-Maturity Debt Securities, Yield	3.10%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 1,799
Held-to-Maturity Securities, Due After Ten Years, Yield	3.10%
Held-to-maturity Securities [Member] | Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	$ 40
Held-to-Maturity Debt Securities, Yield	1.70%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 39
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield	1.60%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 1
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield	3.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 0
Held-to-Maturity Securities, Due After Ten Years, Yield	0.00%

Investment Securities (Invest64

Investment Securities (Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Taxable interest	$ 141	$ 93	$ 390	$ 276
Taxable dividends	3	4	8	13
Interest and dividends exempt from U.S. federal income tax	6	4	17	13
Interest and Dividend Income, Securities, Operating, Available-for-sale	157	101	437	302
Excludes Other Earning Assets [Member]
Interest and Dividend Income, Securities, Operating, Available-for-sale	$ 150	$ 101	$ 415	$ 302

Investment Securities (Schedule

Investment Securities (Schedule Of Realized Gain (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Available-for-sale Securities [Abstract]
Available-for-sale Securities, Gross Realized Gains	$ 24	$ 52	$ 75	$ 146
Available-for-sale Securities, Gross Realized Losses	(1)	0	(2)	(1)
Available-for-sale Securities, Gross Realized Gain (Loss)	$ 23	$ 52	$ 73	$ 145

Investment Securities (Schedu66

Investment Securities (Schedule of Unrealized Loss on Investments) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	$ 10,959	$ 12,356
Available-for-sale Securities, Unrealized Loss Less than 12 months	(178)	(317)
Available-for-sale Securities, Fair value 12 months or longer	2,021	2,038
Available-for-sale Securities, Unrealized Loss 12 months or longer	(101)	(118)
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	10,858	12,205
Available-for-sale Securities, Unrealized Loss Less than 12 months	(170)	(309)
Available-for-sale Securities, Fair value 12 months or longer	1,902	1,769
Available-for-sale Securities, Unrealized Loss 12 months or longer	(59)	(72)
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	2,029	1,612
Available-for-sale Securities, Unrealized Loss Less than 12 months	(39)	(60)
Available-for-sale Securities, Fair value 12 months or longer	0	0
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	0
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	311	524
Available-for-sale Securities, Unrealized Loss Less than 12 months	(4)	(19)
Available-for-sale Securities, Fair value 12 months or longer	138	0
Available-for-sale Securities, Unrealized Loss 12 months or longer	(6)	0
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	78	38
Available-for-sale Securities, Unrealized Loss Less than 12 months	(2)	0
Available-for-sale Securities, Fair value 12 months or longer	0	0
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	7,444	8,052
Available-for-sale Securities, Unrealized Loss Less than 12 months	(115)	(196)
Available-for-sale Securities, Fair value 12 months or longer	730	587
Available-for-sale Securities, Unrealized Loss 12 months or longer	(18)	(16)
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	103	813
Available-for-sale Securities, Unrealized Loss Less than 12 months	(1)	(17)
Available-for-sale Securities, Fair value 12 months or longer	825	860
Available-for-sale Securities, Unrealized Loss 12 months or longer	(31)	(53)
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	164	47
Available-for-sale Securities, Unrealized Loss Less than 12 months	(2)	(1)
Available-for-sale Securities, Fair value 12 months or longer	15	149
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	(1)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	341	375
Available-for-sale Securities, Unrealized Loss Less than 12 months	(1)	(2)
Available-for-sale Securities, Fair value 12 months or longer	86	127
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	0
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	388	744
Available-for-sale Securities, Unrealized Loss Less than 12 months	(6)	(14)
Available-for-sale Securities, Fair value 12 months or longer	108	46
Available-for-sale Securities, Unrealized Loss 12 months or longer	(4)	(2)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	101	151
Available-for-sale Securities, Unrealized Loss Less than 12 months	(8)	(8)
Available-for-sale Securities, Fair value 12 months or longer	119	269
Available-for-sale Securities, Unrealized Loss 12 months or longer	$ (42)	$ (46)

Finance Receivables and Loans67

Finance Receivables and Loans, Net (Schedule of Accounts, Notes, Loans and Financing Receivables) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 118,871		$ 118,944	$ 114,959
Derivative, Amount of Hedged Item	274		315
Loans and Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	494		359
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	79,092		76,843
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	67,077		65,793	64,816
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Derivative, Amount of Hedged Item	24		43
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	12,015		11,050	10,857
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	9,760		8,294
Held For Investment Mortgage Finance Receivables Interest Only Mortgage Loans	$ 24		30
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | Two years and six months, or less [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest-only mortgage loan portfolio principal amortization	35.00%
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | Three years and six months, or less [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest-only mortgage loan portfolio principal amortization	44.00%
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 2,255		2,756
Held For Investment Mortgage Finance Receivables Interest Only Mortgage Loans		$ 538	714
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member] | One year and six months, or less [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest-only mortgage loan portfolio principal amortization	2.00%
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member] | Four years and six months, or greater [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest-only mortgage loan portfolio principal amortization		1.00%
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 39,779		42,101	$ 39,286
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	31,985		35,041
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	3,774		3,248
Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 4,020		$ 3,812

Finance Receivables and Loans68

Finance Receivables and Loans, Net (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Financing Receivable, Allowance for Credit Losses	$ 1,225	$ 1,089	$ 1,144	$ 1,054
Allowance for Loan and Lease Losses, Write-offs	(344)	(303)	(990)	(803)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	91	90	285	259
Allowance for Loan and Lease Losses Write-offs, Net	(253)	(213)	(705)	(544)
Provision for Loan Losses Expensed	314	258	854	650
Allowance for Loan and Lease Losses, Adjustments, Other	0		7	26
Financing Receivable, Allowance for Credit Losses	1,286	1,134	1,286	1,134
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	86	84	86	84
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,200	1,050	1,200	1,050
Loans and Leases Receivable, Gross	118,871	114,959	118,871	114,959	$ 118,944
Financing Receivable, Individually Evaluated for Impairment	786	711	786	711
Financing Receivable, Collectively Evaluated for Impairment	118,085	114,248	118,085	114,248
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Financing Receivable, Allowance for Credit Losses	1,002	862	932	834
Allowance for Loan and Lease Losses, Write-offs	(327)	(293)	(958)	(773)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	85	74	266	233
Allowance for Loan and Lease Losses Write-offs, Net	(242)	(219)	(692)	(540)
Provision for Loan Losses Expensed	314	269	841	644
Allowance for Loan and Lease Losses, Adjustments, Other	0		7	26
Financing Receivable, Allowance for Credit Losses	1,074	912	1,074	912
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	35	24	35	24
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,039	888	1,039	888
Loans and Leases Receivable, Gross	67,077	64,816	67,077	64,816	65,793
Financing Receivable, Individually Evaluated for Impairment	403	349	403	349
Financing Receivable, Collectively Evaluated for Impairment	66,674	64,467	66,674	64,467
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Financing Receivable, Allowance for Credit Losses	83	109	91	114
Allowance for Loan and Lease Losses, Write-offs	(7)	(10)	(22)	(29)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	6	16	19	25
Allowance for Loan and Lease Losses Write-offs, Net	(1)	6	(3)	(4)
Provision for Loan Losses Expensed	0	(15)	(6)	(10)
Allowance for Loan and Lease Losses, Adjustments, Other	1		1	0
Financing Receivable, Allowance for Credit Losses	81	100	81	100
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	30	35	30	35
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	51	65	51	65
Loans and Leases Receivable, Gross	12,015	10,857	12,015	10,857	11,050
Financing Receivable, Individually Evaluated for Impairment	237	251	237	251
Financing Receivable, Collectively Evaluated for Impairment	11,778	10,606	11,778	10,606
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Financing Receivable, Allowance for Credit Losses	140	118	121	106
Allowance for Loan and Lease Losses, Write-offs	(10)	0	(10)	(1)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	0	0	0	1
Allowance for Loan and Lease Losses Write-offs, Net	(10)	0	(10)	0
Provision for Loan Losses Expensed	0	4	19	16
Allowance for Loan and Lease Losses, Adjustments, Other	(1)		(1)	0
Financing Receivable, Allowance for Credit Losses	131	122	131	122
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	21	25	21	25
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	110	97	110	97
Loans and Leases Receivable, Gross	39,779	39,286	39,779	39,286	$ 42,101
Financing Receivable, Individually Evaluated for Impairment	146	111	146	111
Financing Receivable, Collectively Evaluated for Impairment	$ 39,633	$ 39,175	$ 39,633	$ 39,175

Finance Receivables and Loans69

Finance Receivables and Loans, Net (Schedule of Sales of Financing Receivables and Loans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Sales and Transfers	$ 31	$ 63	$ 1,335	$ 4,256
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Sales and Transfers	28	57	1,326	4,216
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Sales and Transfers	3	6	9	12
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Sales and Transfers	$ 0	$ 0	$ 0	$ 28

Finance Receivables and Loans70

Finance Receivables and Loans, Net Finance Receivables and Loans, Net (Schedule of Purchases of Financing Receivables and Loans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Purchases	$ 1,266	$ 467	$ 3,081	$ 2,855
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Purchases	83	0	762	0
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Purchases	$ 1,183	$ 467	$ 2,319	$ 2,855

Finance Receivables and Loans71

Finance Receivables and Loans, Net (Past Due Financing Receivables and Loans) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 2,657	$ 2,759
Financing Receivable, Recorded Investment, Current	116,214	116,185
Loans and Leases Receivable, Gross	118,871	118,944	$ 114,959
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,617	2,749
Financing Receivable, Recorded Investment, Current	76,475	74,094
Loans and Leases Receivable, Gross	79,092	76,843
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,417	2,580
Financing Receivable, Recorded Investment, Current	64,660	63,213
Loans and Leases Receivable, Gross	67,077	65,793	64,816
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	200	169
Financing Receivable, Recorded Investment, Current	11,815	10,881
Loans and Leases Receivable, Gross	12,015	11,050	10,857
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	81	49
Financing Receivable, Recorded Investment, Current	9,679	8,245
Loans and Leases Receivable, Gross	9,760	8,294
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	119	120
Financing Receivable, Recorded Investment, Current	2,136	2,636
Loans and Leases Receivable, Gross	2,255	2,756
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	40	10
Financing Receivable, Recorded Investment, Current	39,739	42,091
Loans and Leases Receivable, Gross	39,779	42,101	$ 39,286
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	29	10
Financing Receivable, Recorded Investment, Current	31,956	35,031
Loans and Leases Receivable, Gross	31,985	35,041
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	8	0
Financing Receivable, Recorded Investment, Current	3,766	3,248
Loans and Leases Receivable, Gross	3,774	3,248
Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	3	0
Financing Receivable, Recorded Investment, Current	4,017	3,812
Loans and Leases Receivable, Gross	4,020	3,812
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,876	1,937
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,857	1,934
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,742	1,850
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	115	84
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	75	39
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	40	45
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	19	3
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	16	3
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	3	0
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	436	452
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	436	452
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	414	428
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	22	24
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1	6
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	21	18
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	345	370
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	324	363
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	261	302
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	63	61
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	5	4
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	58	57
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	21	7
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	13	7
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	8	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 0	$ 0

Finance Receivables and Loans72

Finance Receivables and Loans, Net (Schedule of Financing Receivables, Non Accrual Status) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 807	$ 819
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	661	697
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	573	598
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	88	99
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	7	10
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	81	89
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	146	122
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	78	33
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	61	84
Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 7	$ 5

Finance Receivables and Loans73

Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 118,871	$ 118,944	$ 114,959
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	79,092	76,843
Consumer Portfolio Segment [Member] | Consumer Loan [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	78,431	76,146
Consumer Portfolio Segment [Member] | Consumer Loan [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	661	697
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	67,077	65,793	64,816
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	66,504	65,195
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	573	598
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	12,015	11,050	$ 10,857
Consumer Portfolio Segment [Member] | Residential Mortgage [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	11,927	10,951
Consumer Portfolio Segment [Member] | Residential Mortgage [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	88	99
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	9,760	8,294
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	9,753	8,284
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	7	10
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,255	2,756
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,174	2,667
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 81	$ 89

Finance Receivables and Loans74

Finance Receivables and Loans, Net (Schedule of Pass And Criticized Credit Quality Indicators of Finance Receivables) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 118,871	$ 118,944	$ 114,959
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	39,779	42,101	$ 39,286
Commercial Portfolio Segment [Member] | Commercial Loan [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	36,993	39,410
Commercial Portfolio Segment [Member] | Commercial Loan [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,786	2,691
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	31,985	35,041
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	30,189	33,160
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,796	1,881
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	3,774	3,248
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,913	2,597
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	861	651
Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	4,020	3,812
Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	3,891	3,653
Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 129	$ 159

Finance Receivables and Loans75

Finance Receivables and Loans, Net (Impaired Financing Receivables) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	$ 808	$ 795
Impaired Financing Receivable, Recorded Investment	786	739
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	210	199
Impaired Financing Receivable, with Related Allowance, Recorded Investment	576	540
Impaired Financing Receivable, Related Allowance	86	85
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	653	658
Impaired Financing Receivable, Recorded Investment	640	617
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	146	190
Impaired Financing Receivable, with Related Allowance, Recorded Investment	494	427
Impaired Financing Receivable, Related Allowance	65	62
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	411	407
Impaired Financing Receivable, Recorded Investment	403	370
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	86	131
Impaired Financing Receivable, with Related Allowance, Recorded Investment	317	239
Impaired Financing Receivable, Related Allowance	35	28
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	242	251
Impaired Financing Receivable, Recorded Investment	237	247
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	60	59
Impaired Financing Receivable, with Related Allowance, Recorded Investment	177	188
Impaired Financing Receivable, Related Allowance	30	34
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	8	8
Impaired Financing Receivable, Recorded Investment	8	8
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4	3
Impaired Financing Receivable, with Related Allowance, Recorded Investment	4	5
Impaired Financing Receivable, Related Allowance	0	0
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	234	243
Impaired Financing Receivable, Recorded Investment	229	239
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	56	56
Impaired Financing Receivable, with Related Allowance, Recorded Investment	173	183
Impaired Financing Receivable, Related Allowance	30	34
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	155	137
Impaired Financing Receivable, Recorded Investment	146	122
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	64	9
Impaired Financing Receivable, with Related Allowance, Recorded Investment	82	113
Impaired Financing Receivable, Related Allowance	21	23
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	78	33
Impaired Financing Receivable, Recorded Investment	78	33
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	51	7
Impaired Financing Receivable, with Related Allowance, Recorded Investment	27	26
Impaired Financing Receivable, Related Allowance	3	3
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	70	99
Impaired Financing Receivable, Recorded Investment	61	84
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	10	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	51	84
Impaired Financing Receivable, Related Allowance	17	19
Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	7	5
Impaired Financing Receivable, Recorded Investment	7	5
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3	2
Impaired Financing Receivable, with Related Allowance, Recorded Investment	4	3
Impaired Financing Receivable, Related Allowance	$ 1	$ 1

Finance Receivables and Loans76

Finance Receivables and Loans, Net (Schedule of Average Balance and Interest Income of Impaired Finance Receivables) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 775	$ 717	$ 746	$ 697
Impaired Financing Receivable, Interest Income, Accrual Method	8	7	32	21
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	628	600	612	598
Impaired Financing Receivable, Interest Income, Accrual Method	7	6	22	19
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	389	347	368	340
Impaired Financing Receivable, Interest Income, Accrual Method	5	4	15	12
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	239	253	244	258
Impaired Financing Receivable, Interest Income, Accrual Method	2	2	7	7
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	8	8	8	8
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	0	0
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	231	245	236	250
Impaired Financing Receivable, Interest Income, Accrual Method	2	2	7	7
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	147	117	134	99
Impaired Financing Receivable, Interest Income, Accrual Method	1	1	10	2
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	77	48	55	35
Impaired Financing Receivable, Interest Income, Accrual Method	1	1	2	1
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	63	63	73	58
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	8	1
Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	7	6	6	6
Impaired Financing Receivable, Interest Income, Accrual Method	$ 0	$ 0	$ 0	$ 0

Finance Receivables and Loans77

Finance Receivables and Loans, Net (Troubled Debt Restructurings) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	$ 715		$ 715		$ 663
Financing Receivable, Modifications, Number of Contracts	7,208	4,464	19,492	14,913
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 100	$ 76	$ 377	$ 254
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 95	$ 64	$ 340	$ 218
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	7,204	4,464	19,486	14,913
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 84	$ 76	$ 317	$ 254
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 79	$ 64	$ 280	$ 218
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	7,165	4,427	19,374	14,816
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 80	$ 70	$ 298	$ 238
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 75	$ 58	$ 262	$ 202
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	39	37	112	97
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 4	$ 6	$ 19	$ 16
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 4	$ 6	$ 18	$ 16
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	2	2	3	5
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 0	$ 0	$ 0	$ 2
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 0	$ 0	$ 0	$ 2
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	37	35	109	92
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 4	$ 6	$ 19	$ 14
Financing Receivable, Modifications, Post-Modification Recorded Investment	4	$ 6	18	$ 14
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Modifications [Line Items]
Loans and Leases Receivable, Impaired, Commitment to Lend	$ 7		$ 7		$ 2
Financing Receivable, Modifications, Number of Contracts	4	0	6	0
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 16	$ 0	$ 60	$ 0
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 16	$ 0	$ 60	$ 0
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	3	0	3	0
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 13	$ 0	$ 13	$ 0
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 13	$ 0	$ 13	$ 0
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts			2	0
Financing Receivable, Modifications, Pre-Modification Recorded Investment			$ 44	$ 0
Financing Receivable, Modifications, Post-Modification Recorded Investment			$ 44	$ 0
Commercial Portfolio Segment [Member] | Commercial Real Estate Automobile [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	1	0	1	0
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 3	$ 0	$ 3	$ 0
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 3	$ 0	$ 3	$ 0

Finance Receivables and Loans78

Finance Receivables and Loans, Net (Finance receivables and loans redefaulted during the period) (Details) - Consumer Portfolio Segment [Member] $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	2,223	1,960	6,356	5,621
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 25	$ 23	$ 75	$ 69
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 18	$ 14	$ 51	$ 39
Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	2,222	1,959	6,354	5,617
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 25	$ 23	$ 74	$ 69
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 18	$ 14	$ 51	$ 39
Mortgage Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0	1	0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 0	$ 0	$ 1	$ 0
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 0	$ 0	$ 0	$ 0
Mortgage - Legacy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	1	1	1	4
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 0	$ 0	$ 0	$ 0
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 0	$ 0	$ 0	$ 0

Investment in Operating Lease79

Investment in Operating Leases, Net (Investments In Operating Leases) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Leases, Operating [Abstract]
Property Subject to or Available for Operating Lease, Gross	$ 11,001	$ 14,584
Property Subject to or Available for Operating Lease, Accumulated Depreciation	(2,070)	(3,114)
Property Subject to or Available for Operating Lease, Net	$ 8,931	$ 11,470

Investment in Operating Lease80

Investment in Operating Leases, Net (Schedule Of Depreciation Expense On Operating Lease Assets) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Leases, Operating [Abstract]
Depreciation Expense On Operating Lease Assets	$ 323	$ 470	$ 1,062	$ 1,555
Gross Remarketing (Gains) Losses	(51)	(62)	(80)	(203)
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	$ 272	$ 408	$ 982	$ 1,352

Securitizations and Variable 81

Securitizations and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale, Gain (Loss) on Sale	$ 0	$ 2
Assets of nonconsolidated variable interest entities	2,293	2,293	$ 2,899
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	3,090	3,090	3,574
Carrying value of assets for VIEs for which we have continuing involvement	30,669	30,669	37,631
Carrying value of liabilities for VIEs for which we have continuing involvement	10,324	10,324	13,490
Commercial Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	575	575	460
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	238	238	169
Assets of nonconsolidated variable interest entities	0	0	0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	756	756	651
Automobile Loan [Member] | Consumer Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	17,462	17,462	20,869
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	7,529	7,529	8,557
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	42	42	24
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	0	0	0
Assets of nonconsolidated variable interest entities	2,293	2,293	2,899
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	2,334	2,334	2,923
Automobile Loan [Member] | Consumer Portfolio Segment [Member] | Held-to-maturity Securities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	40	40
Automobile Loan [Member] | Consumer Portfolio Segment [Member] | Other Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	2	2
Automobile Loan [Member] | Commercial Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	12,590	12,590	16,278
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	2,557	2,557	4,764
Unencumbered [Member] | Automobile Loan [Member] | Consumer Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	8,423	8,423	9,600
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 30	$ 30	$ 50

Securitizations and Variable 82

Securitizations and Variable Interest Entities (Schedule of Cash Flow Received from and Paid to Nonconsolidated Securitization Entities) (Details) - Consumer Portfolio Segment [Member] - Automobile Loan [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash Flow Received and Paid to Nonconsolidated Securitization Entities [Line Items]
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers	$ 1,187	$ 1,659
Cash Flows Between Transferor and Transferee, Purchases of Previously Transferred Financial Assets	(491)
Cash Flows Between Transferor and Transferee, Servicing Fees	25	27
Cash Flows Between Transferor and Transferee, Beneficial Interest	16
Cash Flows Between Transferor and Transferee, Receipts on Transferor's Interest in Transferred Financial Assets, Other	$ 4	$ 6

Securitizations and Variable 83

Securitizations and Variable Interest Entities (Schedule of Quantitative Information and Net Credit Losses about Securitized and Other Financial Assets Managed Together) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	$ 122,819		$ 122,819		$ 124,500
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	799		799		841
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	257	$ 216	717	$ 552
On-Balance Sheet Loans [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	118,871		118,871		118,944
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	781		781		822
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	253	213	705	544
On-Balance Sheet Loans [Member] | Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	67,077		67,077		65,793
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	675		675		730
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	242	219	692	540
On-Balance Sheet Loans [Member] | Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	12,015		12,015		11,050
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	85		85		85
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	(6)	3	4
On-Balance Sheet Loans [Member] | Commercial Portfolio Segment [Member] | Automobile Loan [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	36,005		36,005		38,853
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	13		13		7
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	0	1	0
On-Balance Sheet Loans [Member] | Commercial Portfolio Segment [Member] | Other Financing Receivables [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	3,774		3,774		3,248
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	8		8		0
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	9	0	9	0
Off-Balance Sheet Loans [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	2,293		2,293		2,392
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	14		14		13
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	3	2	9	6
Off-Balance Sheet Loans [Member] | Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	2,293		2,293		2,392
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	14		14		13
Whole-Loan Transactions [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	1,655		1,655		3,164
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	4		4		$ 6
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	$ 1	$ 1	$ 3	$ 2

Servicing Activities (Schedule

Servicing Activities (Schedule of Total Serviced Automobile Loans Outstanding) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Automobile Serviced Assets [Line Items]
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	$ 11	$ 18	$ 41	$ 49
Total Primary Serviced Assets	115,630		115,630		$ 121,480
Consumer Loan [Member] | On-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	66,721		66,721		65,646
Commercial Loan [Member] | On-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	36,005		36,005		38,853
Operating Leases [Member] | On-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	8,853		8,853		11,311
Other Assets [Member] | On-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	71		71		67
Asset-backed Securities, Securitized Loans and Receivables [Member] | Off-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	2,312		2,312		2,412
Whole-Loan Transactions [Member] | Off-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	$ 1,668		$ 1,668		$ 3,191

Other Assets (Schedule of Other

Other Assets (Schedule of Other Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Aug. 01, 2016	Jun. 01, 2016
Goodwill [Line Items]
Goodwill	$ 240	$ 240
Property, Plant and Equipment, Gross	1,024	901
Accumulated depreciation	(587)	(525)
Property, Plant and Equipment, Net	437	376
Restricted cash collections for securitization trusts	1,260	1,694
Nonmarketable equity securities	1,065	1,046
Deferred Tax Assets, Net	659	994
Interest Receivable	508	476
Goodwill	240	240
Accounts and Other Receivables, Net, Current	212	100
Cash reserve deposits held for securitization trusts	120	184
Restricted Cash and Cash Equivalents	112	111
Derivative Asset, Fair Value, Gross Asset	37	95
Cash and securities collateral placed with counterparties	20	167
Other Assets, Miscellaneous	1,393	1,371
Other Assets	6,063	6,854
Federal Home Loan Bank Stock	581	577
Federal Reserve Bank Stock	445	435
Insurance Operations Member
Goodwill [Line Items]
Goodwill	27	27
Goodwill	27	27
Corporate and Other [Member]
Goodwill [Line Items]
Goodwill	193	193		$ 193
Goodwill	193	193		$ 193
Automotive Finance Operations [Member]
Goodwill [Line Items]
Goodwill	20	20	$ 20
Goodwill	$ 20	$ 20	$ 20

Deposit Liabilities (Schedule o

Deposit Liabilities (Schedule of Deposit Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Deposits [Abstract]
Noninterest-bearing deposit liabilities	$ 129	$ 84
Interest-bearing Deposit Liabilities, by Component [Abstract]
Deposits, Savings Deposits	50,287	46,976
Time Deposits	39,686	31,795
Dealer deposits	14	167
Deposits	90,116	79,022
Time Deposits, $100,000 or More	16,200	12,100
Time Deposits, at or Above FDIC Insurance Limit	$ 4,500	$ 3,500

Debt Debt (Schedule of Short-te

Debt Debt (Schedule of Short-term Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Demand Notes	$ 3,379	$ 3,622
Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months	5,625	7,875
Securities Sold under Agreements to Repurchase, Gross	1,171	1,176
Short-term Debt	10,175	12,673
Non-derivative Cash Collateral Placed with Counterparties Associated with the Repurchase Agreements	10	45
Unsecured Debt [Member]
Short-term Debt [Line Items]
Demand Notes	3,379	3,622
Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months	0	0
Securities Sold under Agreements to Repurchase, Gross	0	0
Short-term Debt	3,379	3,622
Secured Debt [Member]
Short-term Debt [Line Items]
Demand Notes	0	0
Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months	5,625	7,875
Securities Sold under Agreements to Repurchase, Gross	1,171	1,176
Short-term Debt	6,796	9,051
Maturity Less than 30 Days [Member] | Secured Debt [Member]
Short-term Debt [Line Items]
U.S. Treasury Securities Sold under Agreements to Repurchase, Maturity Period	537
Mortgage-backed Residential Securities Sold under Agreements to Repurchase, Maturity Period	480
Maturity less than 60 Days [Member] | Secured Debt [Member]
Short-term Debt [Line Items]
Mortgage-backed Residential Securities Sold under Agreements to Repurchase, Maturity Period	634
Maturity 31 to 60 Days [Member] | Secured Debt [Member]
Short-term Debt [Line Items]
Mortgage-backed Residential Securities Sold under Agreements to Repurchase, Maturity Period	$ 154
One year, or less [Member] | Secured Debt [Member]
Short-term Debt [Line Items]
Asset-backed Automotive Financial Securities Sold under Agreements to Repurchase, Maturity Period		$ 500

Debt (Schedule of Debt) (Detail

Debt (Schedule of Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	$ 10,470	$ 14,553
Long-term Debt, Excluding Current Maturities	34,378	39,260
Derivative, Amount of Hedged Item	274	315
Long-term debt	45,122	54,128
Secured Debt	34,672	43,129
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	3,828	4,274
Long-term Debt, Excluding Current Maturities	13,129	15,450
Derivative, Amount of Hedged Item	289	326
Long-term debt	17,246	20,050
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	6,642	10,279
Long-term Debt, Excluding Current Maturities	21,249	23,810
Derivative, Amount of Hedged Item	(15)	(11)
Long-term debt	27,876	34,078
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	2,600	2,600
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Secured Debt	$ 8,400	$ 6,100

Debt (Scheduled Remaining Matur

Debt (Scheduled Remaining Maturity of Long-term Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 2,614
Long-term Debt, Maturities, Repayments of Principal in Year Two	10,861
Long-term Debt, Maturities, Repayments of Principal in Year Three	9,258
Long-term Debt, Maturities, Repayments of Principal in Year Four	9,031
Long-term Debt, Maturities, Repayments of Principal in Year Five	3,773
Long-term Debt, Maturities, Repayments of Principal after Year Five	9,311
Derivative, Amount of Hedged Item	274	$ 315
Long-term debt	45,122	54,128
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	1,566
Long-term Debt, Maturities, Repayments of Principal in Year Two	3,482
Long-term Debt, Maturities, Repayments of Principal in Year Three	1,641
Long-term Debt, Maturities, Repayments of Principal in Year Four	2,213
Long-term Debt, Maturities, Repayments of Principal in Year Five	594
Long-term Debt, Maturities, Repayments of Principal after Year Five	7,461
Derivative, Amount of Hedged Item	289	326
Long-term debt	17,246	20,050
Secured Debt [Member]
Debt Instrument [Line Items]
Derivative, Amount of Hedged Item	(15)	(11)
Long-term debt	27,876	$ 34,078
Long-term Debt [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	1,590
Long-term Debt, Maturities, Repayments of Principal in Year Two	3,582
Long-term Debt, Maturities, Repayments of Principal in Year Three	1,680
Long-term Debt, Maturities, Repayments of Principal in Year Four	2,252
Long-term Debt, Maturities, Repayments of Principal in Year Five	637
Long-term Debt, Maturities, Repayments of Principal after Year Five	8,475
Derivative, Amount of Hedged Item	289
Long-term debt	18,505
Long-term Debt [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	1,048
Long-term Debt, Maturities, Repayments of Principal in Year Two	7,379
Long-term Debt, Maturities, Repayments of Principal in Year Three	7,617
Long-term Debt, Maturities, Repayments of Principal in Year Four	6,818
Long-term Debt, Maturities, Repayments of Principal in Year Five	3,179
Long-term Debt, Maturities, Repayments of Principal after Year Five	1,850
Derivative, Amount of Hedged Item	(15)
Long-term debt	27,876
original issue discount [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Derivative, Amount of Hedged Item	0
Debt Instrument, Unamortized Discount	(24)
Debt Instrument, Unamortized Discount	(1,259)
original issue discount [Member] | Unsecured Debt [Member] | Debt Instrument, Redemption, Period One [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount, Noncurrent	(100)
original issue discount [Member] | Unsecured Debt [Member] | Debt Instrument, Redemption, Period Two [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount, Noncurrent	(39)
original issue discount [Member] | Unsecured Debt [Member] | Debt Instrument, Redemption, Period Three [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount, Noncurrent	(39)
original issue discount [Member] | Unsecured Debt [Member] | Debt Instrument, Redemption, Period Four [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount, Noncurrent	(43)
original issue discount [Member] | Unsecured Debt [Member] | Debt Instrument, Redemption, Period Five [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount, Noncurrent	$ (1,014)

Debt (Pledged Assets Related to

Debt (Pledged Assets Related to Secured Borrowings and Repurchase Agreement) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Pledged Assets related to secured borrowings [Line Items]
Pledged Financial Instruments, Not Separately Reported, Other Debt Securities Available-for-sale or Held-for-investment	$ 6,676	$ 4,895
Pledged Assets, Mortgage assets held for investment	11,888	10,954
Pledged Assets, Investment in operating leases	737	2,040
Pledged Assets, Other, Not Separately Reported on Statement of Financial Position	56,704	65,222
Secured Debt	34,672	43,129
Short-term Debt	10,175	12,673
Ally Bank [Member]
Pledged Assets related to secured borrowings [Line Items]
Pledged Financial Instruments, Not Separately Reported, Other Debt Securities Available-for-sale or Held-for-investment	5,482	4,231
Pledged Assets, Mortgage assets held for investment	11,888	10,954
Pledged Assets, Investment in operating leases	7	913
Pledged Assets, Other, Not Separately Reported on Statement of Financial Position	38,213	41,129
Secured Debt	18,781	22,149
Pledged assets for Federal Home Loan Bank [Member] | Ally Bank [Member]
Pledged Assets related to secured borrowings [Line Items]
Pledged Assets, Other, Not Separately Reported on Statement of Financial Position	21,400	19,000
Pledged assets for Federal Reserve Bank [Member] | Ally Bank [Member]
Pledged Assets related to secured borrowings [Line Items]
Pledged Assets, Other, Not Separately Reported on Statement of Financial Position	2,300	2,400
Secured Debt [Member]
Pledged Assets related to secured borrowings [Line Items]
Short-term Debt	6,796	9,051
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Pledged Assets related to secured borrowings [Line Items]
Pledged Assets, Not Separately Reported, Finance Receivables	21,261	27,846
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Ally Bank [Member]
Pledged Assets related to secured borrowings [Line Items]
Pledged Assets, Not Separately Reported, Finance Receivables	4,818	5,751
Commercial Portfolio Segment [Member] | Automobile Loan [Member]
Pledged Assets related to secured borrowings [Line Items]
Pledged Assets, Not Separately Reported, Finance Receivables	16,142	19,487
Commercial Portfolio Segment [Member] | Automobile Loan [Member] | Ally Bank [Member]
Pledged Assets related to secured borrowings [Line Items]
Pledged Assets, Not Separately Reported, Finance Receivables	$ 16,018	$ 19,280

Debt Debt (Narrative - Trust Pr

Debt Debt (Narrative - Trust Preferred Securities) (Details) $ / shares in Units, $ in Billions	Sep. 30, 2017USD ($)$ / shares
Narrative - Trust Preferred Securities [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.125%
Preferred Stock, Liquidation Preference Per Share | $ / shares	$ 25
From and including February 15, 2016, to but excluding February 15, 2040, distributions will be payable at an annual rate equal to three-month London interbank offer rate plus:	5.785%
Ally has the right to defer payments of interest for a period not exceeding consecutive quarters of:	20
Percent of principle debt, plus accrued and unpaid interest is the redemption price if Ally redeems the Series 2 TRUPS on or after February 15, 2016.	100.00%
Fixed Income Interest Rate [Member]
Narrative - Trust Preferred Securities [Line Items]
Trust preferred securities | $	$ 2.6

Debt (Committed Funding Facilit

Debt (Committed Funding Facilities) (Details) - Committed Funding Facilities Member - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Outstanding Revolving Funding Facilities	$ 14,700
Line of Credit Facility, Maximum Borrowing Capacity	14,675	$ 18,375
Long-term Line of Credit	9,530	14,800
Line of Credit Facility, Remaining Borrowing Capacity	5,145	3,575
Bank Funding Member | Secured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	3,675	3,600
Long-term Line of Credit	1,350	3,250
Line of Credit Facility, Remaining Borrowing Capacity	2,325	350
Revolving secured funding facilities 1 year or greater [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,600
Nonbank Funding Member | Secured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	11,000	13,525
Long-term Line of Credit	8,180	11,550
Line of Credit Facility, Remaining Borrowing Capacity	2,820	1,975
Nonbank Funding Member | Unsecured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	0	1,250
Long-term Line of Credit	0	0
Line of Credit Facility, Remaining Borrowing Capacity	$ 0	$ 1,250

Accrued Expenses and Other Li93

Accrued Expenses and Other Liabilities (Schedule of Accrued Expenses and Other Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Accounts Payable and Accrued Liabilities [Abstract]
Accounts Payable	$ 863	$ 649
Accrued Employee Benefits	227	232
Liability for Claims and Claims Adjustment Expense	173	149	$ 150	$ 169
Deferred Revenue	34	56
Derivative Liability, Fair Value, Gross Liability	30	95
Cash collateral received from counterparties	14	10
Other Accrued Liabilities	551	546
Accounts Payable and Accrued Liabilities	$ 1,892	$ 1,737

Accumulated Other Comprehensi94

Accumulated Other Comprehensive (Loss) Income (Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax [Abstract]
Beginning Balance Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax			$ (273)	$ (159)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	$ 46	$ (4)	142	258
Ending Balance Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(131)	99	(131)	99
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax [Abstract]
Beginning Balance Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax			14	9
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax			2	5
Ending Balance Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	16	14	16	14
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Beginning Balance Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax			8	8
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax			1	0
Ending Balance Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	9	8	9	8
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			1	1
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax [Abstract]
Beginning Balance Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax			(90)	(89)
Ending Balance Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(91)	(90)	(91)	(90)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax			(341)	(231)
Other Comprehensive Income (Loss), Net of Tax	48	(4)	144	262
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (197)	$ 31	$ (197)	$ 31

Accumulated Other Comprehensi95

Accumulated Other Comprehensive (Loss) Income (Before and After Tax) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, [Abstract]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	$ 95	$ 41	$ 278	$ 506
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	25	52	75	145
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax	70	(11)	203	361
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax [Abstract]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	(22)	(4)	(64)	(133)
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax	(24)	7	(61)	(103)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax [Abstract]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	2	(11)	(3)	(30)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	73	37	214	373
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	27	41	72	115
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	46	(4)	142	258
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax and reclassification adjustments				10
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax				(1)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax	8	(2)	14	11
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment before reclassification adjustments, Tax				4
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Tax				0
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	3	(1)	5	4
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period before reclassification adjustments, Net of Tax				6
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax				(1)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	5	(1)	9	7
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax [Abstract]
Other Comprehensive Income Unrealized Gain Loss On Net Investment Hedges Arising During the Period, Before Tax	(6)	2	(12)	(4)
Other Comprehensive Income Unrealized Gain Loss On Cash Flow Hedges Arising During the Period, Before Tax	1		2
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax Effect [Abstract]
Other Comprehensive Income Unrealized Gain Loss On Net Investment Hedges Arising During the Period, Tax	3	(1)	5	2
Other Comprehensive Income Unrealized Gain Loss On Cash Flow Hedges Arising During the Period, Tax	1		1
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax			1	0
Other Comprehensive Income Unrealized Gain Loss On Net Cash Flow Hedges Arising During the Period Net of Tax	0
Other Comprehensive Income Unrealized Gain Loss On Net Investment Hedges Arising During the Period Net of Tax	(3)	1	(7)	(2)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax			(1)	(1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax			0	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax			(1)	(1)
Other Comprehensive Income (Loss), before Tax [Abstract]
Other Comprehensive Income (Loss), before Tax	73	(11)	206	367
Other Comprehensive Income (Loss), Tax [Abstract]
Other Comprehensive Income (Loss), Tax	25	(7)	62	105
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), Net of Tax	$ 48	$ (4)	$ 144	$ 262

Earnings per Common Share (Sche

Earnings per Common Share (Schedule of Basic and Diluted Earnings per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	$ 280	$ 261	$ 747	$ 865
Dividends, Preferred Stock, Cash	0	0	0	(30)
Net Income (Loss) from Continuing Operations Available to Common Shareholders, Basic	280	261	747	835
Net Income (Loss) from Continuing Operations Available to Common Shareholders, Diluted	280	261	747	835
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	2	(52)	1	(46)
Net Income (Loss) Available to Common Stockholders, Basic	282	209	748	789
Net Income (Loss) Available to Common Stockholders, Diluted	$ 282	$ 209	$ 748	$ 789
Weighted Average Number of Shares Outstanding, Basic	449,169	482,393	457,612	483,993
Weighted Average Number of Shares Outstanding, Diluted	451,078	483,575	458,848	484,762
Earnings Per Share, Basic [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.62	$ 0.54	$ 1.63	$ 1.73
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	(0.11)	0	(0.10)
Earnings Per Share, Basic	0.63	0.43	1.63	1.63
Earnings Per Share, Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Diluted Share	0.62	0.54	1.63	1.72
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	(0.11)	0	(0.10)
Earnings Per Share, Diluted	$ 0.63	$ 0.43	$ 1.63	$ 1.63

Regulatory Capital and Other 97

Regulatory Capital and Other Regulatory Matters (Schedule of Regulatory Capital Amount and Ratios) (Details) - USD ($) $ / shares in Units, $ in Millions	Sep. 30, 2017	Aug. 22, 2017	Jun. 28, 2017	Dec. 31, 2016	Jun. 29, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Required for Capital Adequacy to Risk-weighted Assets	4.50%
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%
Common equity Tier 1 capital conservation buffer	2.50%
Federal Reserve Bank Stock	$ 445			$ 435
Intercompany Dividend	2,900
Assets greater than $50 billion	$ 50,000
Increase (Decrease) in Dividends Payable	50.00%
FRB Approved Capital Action - Dividends			$ 0.12		$ 0.08
Increase (decrease) in share repurchase program	9.00%
2017 through 2018 [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Stock Repurchase Program, Authorized Amount	$ 760
Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Required for Capital Adequacy to Risk-weighted Assets	4.50%
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%
Common Equity Tier 1 Capital	$ 13,175			$ 12,978
Percentage of Common Equity Tier 1 Capital to Risk-weighted Assets	9.72%			9.37%
Tier One Risk Based Capital	$ 15,539			$ 15,147
Tier One Risk Based Capital to Risk Weighted Assets	11.46%			10.93%
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.00%
Capital	$ 17,891			$ 17,419
Capital to Risk Weighted Assets	13.19%			12.57%
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%
Tier One Leverage Capital	$ 15,539			$ 15,147
Tier One Leverage Capital to Average Assets	9.51%			9.54%
Subsidiaries [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Required for Capital Adequacy to Risk-weighted Assets	4.50%
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	15.00%
Common Equity Tier 1 Capital	$ 16,454			$ 17,888
Percentage of Common Equity Tier 1 Capital to Risk-weighted Assets	15.39%			16.70%
Common Equity Tier 1 Capital Required to be Well Capitalized to Risk-weighted Assets	6.50%
Tier One Risk Based Capital	$ 16,454			$ 17,888
Tier One Risk Based Capital to Risk Weighted Assets	15.39%			16.70%
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%
Capital	$ 17,215			$ 18,458
Capital to Risk Weighted Assets	16.10%			17.24%
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%
Tier One Leverage Capital	$ 16,454			$ 17,888
Tier One Leverage Capital to Average Assets	12.89%			15.21%
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%

Regulatory Capital and Other 98

Regulatory Capital and Other Regulatory Matters Regulatory Capital and Other Regulatory Matters (Common Share Repurchases) (Details) - USD ($) $ / shares in Units, $ in Millions	Oct. 10, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value		$ 920			$ 357
Common Stock, Shares, Outstanding		443,796,233			467,000,306
Dividends Payable, Amount Per Share	$ 0.12	$ 0.12
Common Share Repurchases, Period One [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value		$ 190
Treasury Stock, Common, Shares		8,507,000
Dividends Payable, Amount Per Share		$ 0.12
Common Share Repurchases, Period Two [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value			$ 204
Treasury Stock, Common, Shares			10,485,000
Dividends Payable, Amount Per Share			$ 0.08
Common Share Repurchases, Period Three [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value				$ 169
Treasury Stock, Common, Shares				8,097,000
Dividends Payable, Amount Per Share				$ 0.08
Common Share Repurchases, Period Four [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value					$ 167
Treasury Stock, Common, Shares					8,745,000
Dividends Payable, Amount Per Share					$ 0.08
Common Share Repurchases, Period Five [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value						$ 159
Treasury Stock, Common, Shares						8,298,000
Dividends Payable, Amount Per Share						$ 0.08
Beginning of Period [Member] | Common Share Repurchases, Period One [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding		452,292,000
Beginning of Period [Member] | Common Share Repurchases, Period Two [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding			462,193,000
Beginning of Period [Member] | Common Share Repurchases, Period Three [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding				467,000,000
Beginning of Period [Member] | Common Share Repurchases, Period Four [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding					475,470,000
Beginning of Period [Member] | Common Share Repurchases, Period Five [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding						483,753,000
End of Period [Member] | Common Share Repurchases, Period One [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding		443,796,233,000
End of Period [Member] | Common Share Repurchases, Period Two [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding			452,292,000
End of Period [Member] | Common Share Repurchases, Period Three [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding				462,193,000
End of Period [Member] | Common Share Repurchases, Period Four [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding					467,000,000
End of Period [Member] | Common Share Repurchases, Period Five [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding						475,470,000

Derivative Instruments and He99

Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash Collateral Placed with Counterparties Excluding Cash Collateral Associated with Repurchase Agreements	$ 10	$ 122
Securities Collateral Placed with Counterparties	145	72
Non-derivative Cash Collateral Placed with Counterparties Associated with the Repurchase Agreements	10	45
Cash Collateral Received from Counterparties, Excluding Collateral Associated with Repurchase Agreements	14	10
Non-cash collateral received	$ 2	$ 6

Derivative Instruments and H100

Derivative Instruments and Hedging Activities (Fair Value Amounts of Derivative Instruments Reported on our Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 37	$ 95
Derivative Liability, Fair Value, Gross Liability	30	95
Derivative, Notional Amount	25,409	34,166
Interest Receivable	508	476
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	4	20
Derivative Liability, Fair Value, Gross Liability	0	21
Derivative, Notional Amount	6,376	4,902
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	19
Derivative Liability, Fair Value, Gross Liability	0	21
Derivative, Notional Amount	6,140	4,731
Hedge notional amount associated with debt maturing in five or more years	3,100
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	3	1
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	176	171
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	31	73
Derivative Liability, Fair Value, Gross Liability	30	73
Derivative, Notional Amount	18,903	29,172
Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	2	1
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	130	92
Equity Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	1
Derivative Liability, Fair Value, Gross Liability	0	1
Derivative, Notional Amount	0	0
Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Receive-fixed Swaps, Fair Value, Gross Asset	0	8
Receive-fixed Swaps, Fair Value, Gross Liability	0	14
Receive-fixed Swaps, Notional Amount	3,100	1,700
Pay-fixed Swaps, Fair Value, Gross Asset	0	10
Pay-fixed Swaps, Fair Value, Gross Liability	0	1
Pay-fixed Swaps, Notional Amount	0	2,800
Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Pay-fixed Swaps, Fair Value, Gross Asset	0
Pay-fixed Swaps, Notional Amount	1,300
Interest Rate Swap [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	0	137
Foreign Exchange Forward [Member] | Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	2	1
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	130	92
Futures and Forwards [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	60	0
Futures and Forwards [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	116	0
Futures and Forwards [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1
Derivative Liability, Fair Value, Gross Liability	0
Derivative, Notional Amount	60
Written Options [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	0
Derivative Liability, Fair Value, Gross Liability	30	73
Derivative, Notional Amount	9,452	14,518
Written Options [Member] | Equity Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	1
Derivative, Notional Amount	0	0
Purchased Options [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	30	73
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	9,335	14,517
Purchased Options [Member] | Equity Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	1
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	0	0
Other Trading [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	33	75
Derivative Liability, Fair Value, Gross Liability	30	74
Derivative, Notional Amount	19,033	29,264
Secured Debt [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Receive-fixed Swaps, Fair Value, Gross Asset	0	0
Receive-fixed Swaps, Fair Value, Gross Liability	0	7
Receive-fixed Swaps, Notional Amount	1,600	240
Derivative assets in net asset position [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	36	87
Interest Receivable	0	7
Derivative assets in net liability positions [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	8
Interest Receivable	0	$ 1
U.S. Treasury Securities [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Pay-fixed Swaps, Fair Value, Gross Asset	0
Pay-fixed Swaps, Fair Value, Gross Liability	0
Pay-fixed Swaps, Notional Amount	$ 225

Derivative Instruments and H101

Derivative Instruments and Hedging Activities (Statement of Gains and Losses on Derivative Instruments Reported in Statement of Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ 0	$ 0	$ (1)	$ (5)
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(3)	(4)	(10)	(13)
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	0	(5)	(2)	(2)
Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	(3)	(1)	(7)	(6)
Equity Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	2	0	0
Interest Income [Member] | Interest Rate Contract [Member] | Losses Related to Amortization of Deferred Basis Adjustments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax		6
Interest Income [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	(17)	(3)	16
Interest Income [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Hedges of Retail Auto Loans Held for Investment [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	4	1	16
Interest Income [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Losses Related to Amortization of Deferred Basis Adjustments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	6		17	15
Interest Income [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Gains Related to Amortization of Deferred Basis Adjustments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	19	23	59	62
Interest Income [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Losses Related to Amortization of Deferred Basis Adjustments (FHLB) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	1		2
Interest and Dividends Income [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(4)	0	(1)	0
Interest Expense [Member] | Interest Rate Contract [Member] | Hedges of Unsecured Debt Held for Investment [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax		7
Interest Expense [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	5	32	(18)	(214)
Interest Expense [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Hedges of Secured Debt [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	1	1	4
Interest Expense [Member] | Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	0	0	0	(2)
Gains on Mortgage and Automotive Loans [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	0	0	1	0
Other Income [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	0	(5)	(3)	(2)
Other Income [Member] | Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	(3)	(1)	(7)	(4)
Other Income [Member] | Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member] | Revaluation of Foreign-Denominated Debt or Receivable [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	3	1	8	4
Employee compensation and benefits [Member] | Equity Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	2	0	0
Earnings on Derivatives [Member] | Interest Income [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	0	16	1	(18)
Earnings on Derivatives [Member] | Interest and Dividends Income [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	4	0	1	0
Earnings on Derivatives [Member] | Interest Expense [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	(5)	$ (31)	19	211
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Interest Rate Contract [Member] | Hedges of Unsecured Debt Held for Investment [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ 7		$ 19	$ 34

Derivative Instruments and H102

Derivative Instruments and Hedging Activities (Derivative Instruments Used in Net Investment Hedge Accounting Relationships) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Cumulative Translation Adjustment, Net of Tax, Period Increase (Decrease)	$ 7	$ 2	$ 14	$ 9
Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	2	0	2	0
Foreign Exchange Contract [Member] | Net Investment Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ (6)	$ 2	$ (12)	$ (4)

Income Taxes Income Taxes (Inco

Income Taxes Income Taxes (Income Tax Expense) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Tax Expense (Benefit)	$ 115	$ 130		$ 350	$ 336
Other Tax Expense (Benefit)			$ 175

Fair Value (Fair Value Measurem

Fair Value (Fair Value Measurements - Recurring Basis) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 23,099	$ 18,926
Available-for-sale, Equity Investment in Any One Industry Did Not Exceed Percentage	15.00%	14.00%
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 23,099	$ 18,926
Mortgages Held-for-sale, Fair Value Disclosure	9
Retained Interest, Fair Value Disclosure	5	29
Derivative Assets	37	95
Assets, Fair Value Disclosure	23,150	19,050
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(30)	(95)
Liabilities, Fair Value Disclosure	(30)	(95)
Fair Value, Measurements, Recurring [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(30)	(94)
Fair Value, Measurements, Recurring [Member] | Other Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		(1)
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	22,574	18,331
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	2,073	1,620
Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	851	782
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	157	162
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	14,344	10,290
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	2,310	2,097
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	509	537
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,039	1,400
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,291	1,443
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	525	595
Fair Value, Measurements, Recurring [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	32	92
Fair Value, Measurements, Recurring [Member] | Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	5	2
Fair Value, Measurements, Recurring [Member] | Other Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	2,606	2,226
Mortgages Held-for-sale, Fair Value Disclosure	0
Retained Interest, Fair Value Disclosure	0	0
Derivative Assets	1	1
Assets, Fair Value Disclosure	2,607	2,227
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	(1)
Liabilities, Fair Value Disclosure	0	(1)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		(1)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	2,081	1,631
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	2,073	1,620
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	8	11
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	525	595
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	1	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	20,493	16,700
Mortgages Held-for-sale, Fair Value Disclosure	0
Retained Interest, Fair Value Disclosure	0	0
Derivative Assets	35	94
Assets, Fair Value Disclosure	20,528	16,794
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(30)	(94)
Liabilities, Fair Value Disclosure	(30)	(94)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	(30)	(94)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	20,493	16,700
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	851	782
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	149	151
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	14,344	10,290
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	2,310	2,097
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	509	537
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,039	1,400
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,291	1,443
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	30	92
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	5	2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Mortgages Held-for-sale, Fair Value Disclosure	9
Retained Interest, Fair Value Disclosure	5	29
Derivative Assets	1	0
Assets, Fair Value Disclosure	15	29
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	1	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	$ 0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		$ 0

Fair Value (Fair Value Measu105

Fair Value (Fair Value Measurements - Reconciliation of Level 3 Assets And Liabilities) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Beginning balance	$ 9	$ 31	$ 29	$ 40
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	1	1	3	4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	49	0	72	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(44)	2	(56)	8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	(2)	(33)	(20)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Assets, Ending balance	15	32	15	32
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	1	0
Loans Held-for-Sale [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Beginning balance	3		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	1		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	49		72
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(44)		(64)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Assets, Ending balance	9		9
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0		0
Retained Interest [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Beginning balance	5	31	29	40
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	1	1	4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	2	8	8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	(2)	(33)	(20)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Assets, Ending balance	5	32	5	32
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	$ 0	0	$ 0
Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Beginning balance	1		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Assets, Ending balance	1		1
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 0		$ 1

Fair Value (Fair Value Measu106

Fair Value (Fair Value Measurements - Nonrecurring Basis) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	$ 18	$ 0
Fair Value, Measurements, Nonrecurring [Member] | Loans held-for-sale, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	9		$ 56
Lower of cost or fair value or valuation reserve allowance	0		0
Fair Value, Measurements, Nonrecurring [Member] | Commercial Finance Receivables And Loans, Automotive [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	29		30
Lower of cost or fair value or valuation reserve allowance	(4)		(7)
Fair Value, Measurements, Nonrecurring [Member] | Commercial Finance Receivables And Loans, Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	35		45
Lower of cost or fair value or valuation reserve allowance	(16)		(17)
Fair Value, Measurements, Nonrecurring [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	64		75
Lower of cost or fair value or valuation reserve allowance	(20)		(24)
Fair Value, Measurements, Nonrecurring [Member] | Repossessed And Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	13		15
Lower of cost or fair value or valuation reserve allowance	(2)		(4)
Fair Value, Measurements, Nonrecurring [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	3		7
Lower of cost or fair value or valuation reserve allowance	0		0
Fair Value, Measurements, Nonrecurring [Member] | Assets, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	89		153
Lower of cost or fair value or valuation reserve allowance	(22)		(28)
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Loans held-for-sale, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Finance Receivables And Loans, Automotive [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Finance Receivables And Loans, Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Repossessed And Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Assets, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Loans held-for-sale, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Finance Receivables And Loans, Automotive [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Finance Receivables And Loans, Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Repossessed And Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Assets, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Loans held-for-sale, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	9		56
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Finance Receivables And Loans, Automotive [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	29		30
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Finance Receivables And Loans, Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	35		45
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial Finance Receivables and Loans, Net, Fair Value	64		75
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Repossessed And Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	13		15
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	3		7
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Assets, Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 89		$ 153

Fair Value (Fair Value of Finan

Fair Value (Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	$ 1,839	$ 839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	18	0
Loans and Leases Receivable, Net Amount	117,585	117,800
Nonmarketable equity securities	1,065	1,046
Deposits	90,116	79,022
Short-term Debt	10,175	12,673
Long-term Debt	45,122	54,128
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	1,839	839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	9
Loans and Leases Receivable, Net Amount	117,585	117,800
Nonmarketable equity securities	1,053	1,046
Deposits	90,116	79,022
Short-term Debt	10,175	12,673
Long-term Debt	45,122	54,128
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	1,807	789
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	9
Loans and Leases Receivable, Net Amount	119,498	118,750
Nonmarketable equity securities	1,052	1,067
Deposits	88,151	78,469
Short-term Debt	10,177	12,675
Long-term Debt	47,656	56,120
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	0	0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Net Amount	0	0
Nonmarketable equity securities	0	0
Deposits	0	0
Short-term Debt	0	0
Long-term Debt	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	1,807	789
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Net Amount	0	0
Nonmarketable equity securities	1,026	1,012
Deposits	0	0
Short-term Debt	0	0
Long-term Debt	29,776	22,036
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	0	0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	9
Loans and Leases Receivable, Net Amount	119,498	118,750
Nonmarketable equity securities	26	55
Deposits	88,151	78,469
Short-term Debt	10,177	12,675
Long-term Debt	17,880	$ 34,084
Equity Securities [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nonmarketable equity securities	12
Equity Securities [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nonmarketable equity securities	$ 35

Offsetting Assets and Liabil108

Offsetting Assets and Liabilities Offsetting Assets and Liabilities (Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 37	$ 95
Derivative Liability, Fair Value, Gross Liability	30	95
Customer Securities for which Entity has Right to Sell or Repledge, Fair Value	2	6
Derivative assets in net asset position [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	36	87
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	36	87
Derivative Asset, Not Subject to Master Netting Arrangement	0	4
Derivative, Collateral, Obligation to Return Cash	(4)	(9)
Derivative Asset	32	74
Derivative assets in net liability positions [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	8
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	8
Derivative Asset, Not Subject to Master Netting Arrangement	0	8
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset	0	0
Derivative assets with no offsetting arrangements [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	1
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1
Derivative Asset, Not Subject to Master Netting Arrangement	0
Derivative, Collateral, Obligation to Return Cash	0
Derivative Asset	1
Total Derivative Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	37	95
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	37	95
Derivative Asset, Not Subject to Master Netting Arrangement	0	12
Derivative, Collateral, Obligation to Return Cash	(4)	(9)
Derivative Asset	33	74
Derivative Liabilities in Net Liability Positions [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Gross Liability	30	91
Derivative Liability, Fair Value, Amount Offset Against Collateral	30	91
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	8
Derivative, Collateral, Right to Reclaim Cash	0	13
Derivative Liability	30	70
Derivative liabilities in net asset positions [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Gross Liability	0	4
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	4
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	4
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability	0	0
Total derivative liabilities excluding repurchase agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Gross Liability	30	95
Derivative Liability, Fair Value, Amount Offset Against Collateral	30	95
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	12
Derivative, Collateral, Right to Reclaim Cash	0	13
Derivative Liability	30	70
Securities sold under agreement to repurchase [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Gross Liability	1,171	676
Derivative Liability, Fair Value, Amount Offset Against Collateral	1,171	676
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	0
Derivative, Collateral, Right to Reclaim Cash	1,171	676
Derivative Liability	0	0
Total Derivative Liabilities [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Liability, Fair Value, Gross Liability	1,201	771
Derivative Liability, Fair Value, Amount Offset Against Collateral	1,201	771
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	12
Derivative, Collateral, Right to Reclaim Cash	1,171	689
Derivative Liability	$ 30	$ 70

Segment Information (Financial

Segment Information (Financial Information Operating Segments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net Financing Revenue	$ 1,081	$ 996	$ 3,127	$ 2,931
Nonoperating Income (Expense)	381	388	1,165	1,138
Revenues	1,462	1,384	4,292	4,069
Provision for Loan Losses Expensed	314	258	854	650
Noninterest Expense	753	735	2,341	2,218
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	395	391	1,097	1,201
Assets	164,013	157,397	164,013	157,397	$ 163,728
Interest Income (Expense), after Provision for Loan Loss	767	738	2,273	2,281
Automotive Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	950	933	2,774	2,758
Nonoperating Income (Expense)	82	74	290	228
Revenues	1,032	1,007	3,064	2,986
Provision for Loan Losses Expensed	312	270	846	649
Noninterest Expense	420	418	1,283	1,255
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	300	319	935	1,082
Assets	112,141	113,669	112,141	113,669
Insurance Operations Member
Segment Reporting Information [Line Items]
Net Financing Revenue	15	14	44	44
Nonoperating Income (Expense)	272	264	781	777
Revenues	287	278	825	821
Provision for Loan Losses Expensed	0	0	0	0
Noninterest Expense	218	222	737	733
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	69	56	88	88
Assets	7,432	7,259	7,432	7,259
Mortgage Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	32	25	98	71
Nonoperating Income (Expense)	2	0	3	0
Revenues	34	25	101	71
Provision for Loan Losses Expensed	4	1	6	4
Noninterest Expense	28	16	77	48
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	2	8	18	19
Assets	9,804	7,933	9,804	7,933
Corporate Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	39	30	121	87
Nonoperating Income (Expense)	5	4	33	14
Revenues	44	34	154	101
Provision for Loan Losses Expensed	3	3	15	12
Noninterest Expense	19	16	57	49
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	22	15	82	40
Assets	3,699	3,232	3,699	3,232
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	45	(6)	90	(29)
Nonoperating Income (Expense)	20	46	58	119
Revenues	65	40	148	90
Provision for Loan Losses Expensed	(5)	(16)	(13)	(15)
Noninterest Expense	68	63	187	133
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	2	(7)	(26)	(28)
Assets	$ 30,937	$ 25,304	$ 30,937	$ 25,304

Parent and Guarantor Condens110

Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	$ 1,486	$ 1,307	$ 4,301	$ 3,807
Interest and Dividend Income, Securities, Operating	157	101	437	302
Interest Income, Deposits with Financial Institutions	11	3	23	10
Operating Leases, Income Statement, Lease Revenue	434	649	1,465	2,119
Total financing revenue and other interest income	2,088	2,060	6,226	6,238
Interest Expense, Deposits	285	212	766	608
Interest Expense, Short-term Borrowings	34	14	94	39
Interest Expense, Long-term Debt	416	430	1,257	1,308
Interest Expense, Related Party	0	0	0	0
Interest Expense	735	656	2,117	1,955
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	272	408	982	1,352
Net Financing Revenue	1,081	996	3,127	2,931
Dividends from Bank Subsidiary	0		0
Dividends From Non Bank Subsidiary	0	0	0	0
Insurance Services Revenue	252	238	720	704
Gain (Loss) on Sales of Loans, Net	15	0	65	4
Gain (Loss) on Extinguishment of Debt	(4)	0	(6)	(4)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	23	52	73	145
Noninterest Income, Other Operating Income	95	98	313	289
Nonoperating Income (Expense)	381	388	1,165	1,138
Revenues	1,462	1,384	4,292	4,069
Provision for Loan Losses Expensed	314	258	854	650
Labor and Related Expense	264	248	814	742
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	65	69	278	287
Other Noninterest Expense	424	418	1,249	1,189
Noninterest Expense	753	735	2,341	2,218
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	395	391	1,097	1,201
Income Tax Expense (Benefit)	115	130	350	336
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	280	261	747	865
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	2	(52)	1	(46)
Undistributed income of bank subsidiaries	0	0	0	0
Undistributed income of nonbank subsidiaries	0	0	0	0
Net Income (Loss) Attributable to Parent	282	209	748	819
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	48	(4)	144	262
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	330	205	892	1,081
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	13	(15)	(57)	(82)
Interest and Dividend Income, Securities, Operating	0	0	0	0
Interest Income, Deposits with Financial Institutions	2	1	6	4
Operating Leases, Income Statement, Lease Revenue	3	4	9	14
Total financing revenue and other interest income	21	(8)	(31)	(56)
Interest Expense, Deposits	0	2	2	6
Interest Expense, Short-term Borrowings	16	10	52	31
Interest Expense, Long-term Debt	278	289	834	868
Interest Expense, Related Party	3	5	12	14
Interest Expense	297	306	900	919
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	3	3	8	11
Net Financing Revenue	(279)	(317)	(939)	(986)
Dividends from Bank Subsidiary	2,900		2,900
Dividends From Non Bank Subsidiary	101	170	528	800
Insurance Services Revenue	0	0	0	0
Gain (Loss) on Sales of Loans, Net	9	(7)	39	(11)
Gain (Loss) on Extinguishment of Debt	(1)		(1)	(2)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	0	0	0	0
Noninterest Income, Other Operating Income	138	298	569	989
Nonoperating Income (Expense)	146	291	607	976
Revenues	2,868	144	3,096	790
Provision for Loan Losses Expensed	161	147	350	295
Labor and Related Expense	17	143	157	430
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	0	0	0	0
Other Noninterest Expense	208	307	709	963
Noninterest Expense	225	450	866	1,393
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	2,482	(453)	1,880	(898)
Income Tax Expense (Benefit)	(135)	(88)	(362)	(196)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	2,617	(365)	2,242	(702)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	4	(47)	6	(39)
Undistributed income of bank subsidiaries	(2,524)	325	(1,760)	932
Undistributed income of nonbank subsidiaries	185	296	260	628
Net Income (Loss) Attributable to Parent	282	209	748	819
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	48	(4)	144	262
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	330	205	892	1,081
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0	0	0
Interest and Dividend Income, Securities, Operating	0	0	0	0
Interest Income, Deposits with Financial Institutions	0	0	0	0
Operating Leases, Income Statement, Lease Revenue	0	0	0	0
Total financing revenue and other interest income	0	0	0	0
Interest Expense, Deposits	0	0	0	0
Interest Expense, Short-term Borrowings	0	0	0	0
Interest Expense, Long-term Debt	0	0	0	0
Interest Expense, Related Party	0	0	0	0
Interest Expense	0	0	0	0
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	0	0	0	0
Net Financing Revenue	0	0	0	0
Dividends from Bank Subsidiary	2,900		2,900
Dividends From Non Bank Subsidiary	0	0	0	0
Insurance Services Revenue	0	0	0	0
Gain (Loss) on Sales of Loans, Net	0	0	0	0
Gain (Loss) on Extinguishment of Debt	0		0	0
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	0	0	0	0
Noninterest Income, Other Operating Income	0	0	0	0
Nonoperating Income (Expense)	0	0	0	0
Revenues	2,900	0	2,900	0
Provision for Loan Losses Expensed	0	0	0	0
Labor and Related Expense	0	0	0	0
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	0	0	0	0
Other Noninterest Expense	0	0	0	0
Noninterest Expense	0	0	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	2,900	0	2,900	0
Income Tax Expense (Benefit)	0	0	0	(82)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	2,900	0	2,900	82
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0	0	0
Undistributed income of bank subsidiaries	(2,524)	325	(1,760)	932
Undistributed income of nonbank subsidiaries	0	0	0	(2)
Net Income (Loss) Attributable to Parent	376	325	1,140	1,012
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	36	(3)	91	143
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	412	322	1,231	1,155
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	1,473	1,322	4,358	3,889
Interest and Dividend Income, Securities, Operating	157	102	439	303
Interest Income, Deposits with Financial Institutions	9	2	17	6
Operating Leases, Income Statement, Lease Revenue	431	645	1,456	2,105
Total financing revenue and other interest income	2,073	2,075	6,280	6,316
Interest Expense, Deposits	286	210	765	602
Interest Expense, Short-term Borrowings	18	4	42	8
Interest Expense, Long-term Debt	138	141	423	440
Interest Expense, Related Party	2	2	10	8
Interest Expense	444	357	1,240	1,058
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	269	405	974	1,341
Net Financing Revenue	1,360	1,313	4,066	3,917
Dividends from Bank Subsidiary	0		0
Dividends From Non Bank Subsidiary	0	0	0	0
Insurance Services Revenue	252	238	720	704
Gain (Loss) on Sales of Loans, Net	6	7	26	15
Gain (Loss) on Extinguishment of Debt	(3)		(5)	(2)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	23	52	73	145
Noninterest Income, Other Operating Income	199	231	635	661
Nonoperating Income (Expense)	477	528	1,449	1,523
Revenues	1,837	1,841	5,515	5,440
Provision for Loan Losses Expensed	153	111	504	355
Labor and Related Expense	247	105	657	312
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	65	69	278	287
Other Noninterest Expense	459	541	1,431	1,586
Noninterest Expense	771	715	2,366	2,185
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	913	1,015	2,645	2,900
Income Tax Expense (Benefit)	250	218	712	614
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	663	797	1,933	2,286
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(2)	(5)	(5)	(7)
Undistributed income of bank subsidiaries	0	0	0	0
Undistributed income of nonbank subsidiaries	0	0	0	0
Net Income (Loss) Attributable to Parent	661	792	1,928	2,279
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	51	(9)	140	234
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	712	783	2,068	2,513
Affiliated Entity [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0	0	0
Interest Income, Deposits with Financial Institutions	0	0	0	0
Affiliated Entity [Member] | Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	2	2	10	8
Interest Income, Deposits with Financial Institutions	1	0	1	0
Affiliated Entity [Member] | Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0	0	0
Interest Income, Deposits with Financial Institutions	0	0	0	0
Affiliated Entity [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	1	2	5	6
Interest Income, Deposits with Financial Institutions	2	2	5	7
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0	0	0
Interest and Dividend Income, Securities, Operating	0	(1)	(2)	(1)
Interest Income, Deposits with Financial Institutions	0	0	0	0
Operating Leases, Income Statement, Lease Revenue	0	0	0	0
Total financing revenue and other interest income	(6)	(7)	(23)	(22)
Interest Expense, Deposits	(1)	0	(1)	0
Interest Expense, Short-term Borrowings	0	0	0	0
Interest Expense, Long-term Debt	0	0	0	0
Interest Expense, Related Party	(5)	(7)	(22)	(22)
Interest Expense	(6)	(7)	(23)	(22)
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	0	0	0	0
Net Financing Revenue	0	0	0	0
Dividends from Bank Subsidiary	(5,800)		(5,800)
Dividends From Non Bank Subsidiary	(101)	(170)	(528)	(800)
Insurance Services Revenue	0	0	0	0
Gain (Loss) on Sales of Loans, Net	0	0	0	0
Gain (Loss) on Extinguishment of Debt	0		0	0
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	0	0	0	0
Noninterest Income, Other Operating Income	(242)	(431)	(891)	(1,361)
Nonoperating Income (Expense)	(242)	(431)	(891)	(1,361)
Revenues	(6,143)	(601)	(7,219)	(2,161)
Provision for Loan Losses Expensed	0	0	0	0
Labor and Related Expense	0	0	0	0
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	0	0	0	0
Other Noninterest Expense	(243)	(430)	(891)	(1,360)
Noninterest Expense	(243)	(430)	(891)	(1,360)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(5,900)	(171)	(6,328)	(801)
Income Tax Expense (Benefit)	0	0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(5,900)	(171)	(6,328)	(801)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0	0	0
Undistributed income of bank subsidiaries	5,048	(650)	3,520	(1,864)
Undistributed income of nonbank subsidiaries	(185)	(296)	(260)	(626)
Net Income (Loss) Attributable to Parent	(1,037)	(1,117)	(3,068)	(3,291)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(87)	12	(231)	(377)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(1,124)	(1,105)	(3,299)	(3,668)
Consolidation, Eliminations [Member] | Affiliated Entity [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	(3)	(4)	(15)	(14)
Interest Income, Deposits with Financial Institutions	$ (3)	$ (2)	$ (6)	$ (7)

Parent and Guarantor Condens111

Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	$ 810		$ 1,547
Interest-bearing Deposits in Banks and Other Financial Institutions	3,614		4,387
Cash and Cash Equivalents, at Carrying Value	4,424		5,934	$ 4,289		$ 6,380
Trading Securities			0
Available-for-sale securities	23,099		18,926
Held-to-maturity securities	1,839		839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	18		0
Loans and Leases Receivable, Gross	118,871		118,944	114,959
Loans to bank subsidiary			0
Loans to nonbank subsidiary	0		0
Financing Receivable, Allowance for Credit Losses	1,286	$ 1,225	1,144	1,134	$ 1,089	1,054
Loans and Leases Receivable, Net Amount	117,585		117,800
Property Subject to or Available for Operating Lease, Net	8,931		11,470
Receivables from bank subsidiary	0		0
Receivables from nonbank subsidiary	0		0
Investment in bank subsidiaries	0		0
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	2,054		1,905
Other Assets	6,063		6,854
Assets	164,013		163,728	157,397
Noninterest-bearing deposit liabilities	129		84
Interest-bearing Deposit Liabilities	89,987		78,938
Deposits	90,116		79,022
Short-term Debt	10,175		12,673
Long-term Debt	45,122		54,128
Debt Payable To Bank Subsidiaries	0		0
Debt Payable To Nonbank Subsidiaries	0		0
Payables to Nonbank Subsidiaries	0		0
Interest payable	552		351
Unearned Premiums	2,583		2,500
Accounts Payable and Accrued Liabilities	1,892		1,737
Liabilities	150,440		150,411
Stockholders' Equity Attributable to Parent	13,573		13,317	13,630		13,439
Liabilities and Equity	164,013		163,728
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	74		720
Interest-bearing Deposits in Banks and Other Financial Institutions	5		100
Cash and Cash Equivalents, at Carrying Value	1,574		820	1,409		1,635
Trading Securities			0
Available-for-sale securities	0		0
Held-to-maturity securities	0		0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Gross	7,694		4,705
Loans to bank subsidiary			1,125
Loans to nonbank subsidiary	788		1,779
Financing Receivable, Allowance for Credit Losses	197		115
Loans and Leases Receivable, Net Amount	8,285		7,494
Property Subject to or Available for Operating Lease, Net	23		42
Receivables from bank subsidiary	59		299
Receivables from nonbank subsidiary	76		107
Investment in bank subsidiaries	16,383		17,727
Investment in nonbank subsidiaries	9,045		10,318
Premiums receivable and other insurance assets	0		0
Other Assets	3,174		4,347
Assets	38,619		41,154
Noninterest-bearing deposit liabilities	0		0
Interest-bearing Deposit Liabilities	14		167
Deposits	14		167
Short-term Debt	3,379		3,622
Long-term Debt	19,969		21,798
Debt Payable To Bank Subsidiaries	84		330
Debt Payable To Nonbank Subsidiaries	952		1,027
Payables to Nonbank Subsidiaries	149		153
Interest payable	278		253
Unearned Premiums	0		0
Accounts Payable and Accrued Liabilities	221		487
Liabilities	25,046		27,837
Stockholders' Equity Attributable to Parent	13,573		13,317
Liabilities and Equity	38,619		41,154
Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	0		0
Interest-bearing Deposits in Banks and Other Financial Institutions	0		0
Cash and Cash Equivalents, at Carrying Value	0		0	0		0
Trading Securities			0
Available-for-sale securities	0		0
Held-to-maturity securities	0		0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Gross	0		0
Loans to bank subsidiary			0
Loans to nonbank subsidiary	0		0
Financing Receivable, Allowance for Credit Losses	0		0
Loans and Leases Receivable, Net Amount	0		0
Property Subject to or Available for Operating Lease, Net	0		0
Receivables from bank subsidiary	0		0
Receivables from nonbank subsidiary	0		0
Investment in bank subsidiaries	16,383		17,727
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	0		0
Other Assets	0		0
Assets	16,383		17,727
Noninterest-bearing deposit liabilities	0		0
Interest-bearing Deposit Liabilities	0		0
Deposits	0		0
Short-term Debt	0		0
Long-term Debt	0		0
Debt Payable To Bank Subsidiaries	0		0
Debt Payable To Nonbank Subsidiaries	0		0
Payables to Nonbank Subsidiaries	0		0
Interest payable	0		0
Unearned Premiums	0		0
Accounts Payable and Accrued Liabilities	0		0
Liabilities	0		0
Stockholders' Equity Attributable to Parent	16,383		17,727
Liabilities and Equity	16,383		17,727
Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	736		827
Interest-bearing Deposits in Banks and Other Financial Institutions	3,609		4,287
Cash and Cash Equivalents, at Carrying Value	4,903		5,515	3,659		5,595
Trading Securities			82
Available-for-sale securities	23,099		19,253
Held-to-maturity securities	1,923		839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	18
Loans and Leases Receivable, Gross	111,177		114,239
Loans to bank subsidiary			0
Loans to nonbank subsidiary	394		626
Financing Receivable, Allowance for Credit Losses	1,089		1,029
Loans and Leases Receivable, Net Amount	110,482		113,836
Property Subject to or Available for Operating Lease, Net	8,908		11,428
Receivables from bank subsidiary	0		0
Receivables from nonbank subsidiary	91		67
Investment in bank subsidiaries	0		0
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	2,085		1,936
Other Assets	4,910		5,085
Assets	156,419		158,041
Noninterest-bearing deposit liabilities	129		84
Interest-bearing Deposit Liabilities	89,973		78,771
Deposits	91,597		78,855
Short-term Debt	6,796		9,051
Long-term Debt	25,153		32,330
Debt Payable To Bank Subsidiaries	0		0
Debt Payable To Nonbank Subsidiaries	788		2,903
Payables to Nonbank Subsidiaries	108		351
Interest payable	274		98
Unearned Premiums	2,583		2,500
Accounts Payable and Accrued Liabilities	3,692		3,911
Liabilities	130,991		129,999
Stockholders' Equity Attributable to Parent	25,428		28,042
Liabilities and Equity	156,419		158,041
Affiliated Entity [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	0		0
Interest-bearing Deposit Liabilities	0
Affiliated Entity [Member] | Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	1,495		0
Interest-bearing Deposit Liabilities	0
Affiliated Entity [Member] | Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	0		0
Interest-bearing Deposit Liabilities	0
Affiliated Entity [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	558		401
Interest-bearing Deposit Liabilities	1,495
Consolidation, Eliminations [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	0		0
Interest-bearing Deposits in Banks and Other Financial Institutions	0		0
Cash and Cash Equivalents, at Carrying Value	(2,053)		(401)	$ (779)		$ (850)
Trading Securities			(82)
Available-for-sale securities	0		(327)
Held-to-maturity securities	(84)		0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Gross	0		0
Loans to bank subsidiary			(1,125)
Loans to nonbank subsidiary	(1,182)		(2,405)
Financing Receivable, Allowance for Credit Losses	0		0
Loans and Leases Receivable, Net Amount	(1,182)		(3,530)
Property Subject to or Available for Operating Lease, Net	0		0
Receivables from bank subsidiary	(59)		(299)
Receivables from nonbank subsidiary	(167)		(174)
Investment in bank subsidiaries	(32,766)		(35,454)
Investment in nonbank subsidiaries	(9,045)		(10,318)
Premiums receivable and other insurance assets	(31)		(31)
Other Assets	(2,021)		(2,578)
Assets	(47,408)		(53,194)
Noninterest-bearing deposit liabilities	0		0
Interest-bearing Deposit Liabilities	0		0
Deposits	(1,495)		0
Short-term Debt	0		0
Long-term Debt	0		0
Debt Payable To Bank Subsidiaries	(84)		(330)
Debt Payable To Nonbank Subsidiaries	(1,740)		(3,930)
Payables to Nonbank Subsidiaries	(257)		(504)
Interest payable	0		0
Unearned Premiums	0		0
Accounts Payable and Accrued Liabilities	(2,021)		(2,661)
Liabilities	(5,597)		(7,425)
Stockholders' Equity Attributable to Parent	(41,811)		(45,769)
Liabilities and Equity	(47,408)		(53,194)
Consolidation, Eliminations [Member] | Affiliated Entity [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	(2,053)		$ (401)
Interest-bearing Deposit Liabilities	$ (1,495)

Parent and Guarantor Condens112

Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statement of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	$ 282	$ 209	$ 748	$ 819
Net Cash Provided by (Used in) Operating Activities			3,373	3,589
Payments to Acquire Available-for-sale Securities			(9,022)	(11,027)
Proceeds from sales of available-for-sale securities			2,926	8,546
Proceeds from maturities and repayment of available-for-sale securities			2,002	2,411
Payments to Acquire Held-to-maturity Securities			(709)	(650)
Proceeds from Sale and Maturity of Held-to-maturity Securities			32	0
Payments to Acquire Loans Held-for-investment			3,125	2,924
Proceeds from Sale of Loans and Leases Held-for-investment			1,323	4,221
Originations and repayments of loans held-for-investment and other			1,021	(5,384)
Purchases of operating lease assets			(2,844)	(2,360)
Disposals of operating lease assets			4,409	4,631
Payments to Acquire Interest in Subsidiaries and Affiliates			0	309
Proceeds from Contributions from Parent			0	0
Returns of contributed capital			0	0
Increase (Decrease) in Restricted Cash			497	622
Increase (Decrease) in Non marketable equity securities			(20)	(401)
Payments for (Proceeds from) Other Investing Activities			(159)	(157)
Net cash provided by investing activities			(3,669)	(2,781)
Proceeds from (Repayments of) Short-term Debt			(2,500)	(1,673)
Increase (Decrease) in Deposits			11,050	9,240
Proceeds from issuance of long-term debt			13,302	11,229
Repayments of long-term debt			(22,376)	(20,758)
Net Change in Debt, Intercompany			0	0
Payments for Repurchase of Redeemable Preferred Stock				696
Payments for Repurchase of Common Stock			(563)	(173)
Payments of Dividends			(130)	(70)
Dividends paid and returns of contributed capital, Intercompany			0	0
Capital contributions from parent			0	0
Net cash (used in) provided by financing activities			(1,217)	(2,901)
Effect of exchange-rate changes on cash and cash equivalents			3	2
Cash and Cash Equivalents, Period Increase (Decrease)			(1,510)	(2,091)
Cash and Cash Equivalents, at Carrying Value			5,934	6,380
Cash and Cash Equivalents, at Carrying Value	4,424	4,289	4,424	4,289
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	282	209	748	819
Net Cash Provided by (Used in) Operating Activities			3,701	709
Payments to Acquire Available-for-sale Securities			0	0
Proceeds from sales of available-for-sale securities			0	0
Proceeds from maturities and repayment of available-for-sale securities			0	0
Payments to Acquire Held-to-maturity Securities			0	0
Proceeds from Sale and Maturity of Held-to-maturity Securities			0
Payments to Acquire Loans Held-for-investment			35	0
Proceeds from Sale of Loans and Leases Held-for-investment			96	0
Originations and repayments of loans held-for-investment and other			259	934
Purchases of operating lease assets			0	0
Disposals of operating lease assets			7	16
Payments to Acquire Interest in Subsidiaries and Affiliates				309
Proceeds from Contributions from Parent			(1,200)	(3,112)
Returns of contributed capital			1,031	2,168
Increase (Decrease) in Restricted Cash			(19)	(136)
Increase (Decrease) in Non marketable equity securities			0	0
Payments for (Proceeds from) Other Investing Activities			(25)	(156)
Net cash provided by investing activities			2,280	1,193
Proceeds from (Repayments of) Short-term Debt			(245)	72
Increase (Decrease) in Deposits			(153)	(36)
Proceeds from issuance of long-term debt			355	1,084
Repayments of long-term debt			(4,125)	(2,279)
Net Change in Debt, Intercompany			(366)	(30)
Payments for Repurchase of Redeemable Preferred Stock				696
Payments for Repurchase of Common Stock			(563)	(173)
Payments of Dividends			(130)	(70)
Dividends paid and returns of contributed capital, Intercompany			0	0
Capital contributions from parent			0	0
Net cash (used in) provided by financing activities			(5,227)	(2,128)
Effect of exchange-rate changes on cash and cash equivalents			0	0
Cash and Cash Equivalents, Period Increase (Decrease)			754	(226)
Cash and Cash Equivalents, at Carrying Value			820	1,635
Cash and Cash Equivalents, at Carrying Value	1,574	1,409	1,574	1,409
Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	376	325	1,140	1,012
Net Cash Provided by (Used in) Operating Activities			2,900	0
Payments to Acquire Available-for-sale Securities			0	0
Proceeds from sales of available-for-sale securities			0	0
Proceeds from maturities and repayment of available-for-sale securities			0	0
Payments to Acquire Held-to-maturity Securities			0	0
Proceeds from Sale and Maturity of Held-to-maturity Securities			0
Payments to Acquire Loans Held-for-investment			0	0
Proceeds from Sale of Loans and Leases Held-for-investment			0	0
Originations and repayments of loans held-for-investment and other			0	0
Purchases of operating lease assets			0	0
Disposals of operating lease assets			0	0
Payments to Acquire Interest in Subsidiaries and Affiliates				0
Proceeds from Contributions from Parent			0	0
Returns of contributed capital			0	8
Increase (Decrease) in Restricted Cash			0	0
Increase (Decrease) in Non marketable equity securities			0	0
Payments for (Proceeds from) Other Investing Activities			0	0
Net cash provided by investing activities			0	8
Proceeds from (Repayments of) Short-term Debt			0	0
Increase (Decrease) in Deposits			0	0
Proceeds from issuance of long-term debt			0	0
Repayments of long-term debt			0	0
Net Change in Debt, Intercompany			0	0
Payments for Repurchase of Redeemable Preferred Stock				0
Payments for Repurchase of Common Stock			0	0
Payments of Dividends			0	0
Dividends paid and returns of contributed capital, Intercompany			(2,900)	(8)
Capital contributions from parent			0	0
Net cash (used in) provided by financing activities			(2,900)	(8)
Effect of exchange-rate changes on cash and cash equivalents			0	0
Cash and Cash Equivalents, Period Increase (Decrease)			0	0
Cash and Cash Equivalents, at Carrying Value			0	0
Cash and Cash Equivalents, at Carrying Value	0	0	0	0
Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	661	792	1,928	2,279
Net Cash Provided by (Used in) Operating Activities			3,019	3,782
Payments to Acquire Available-for-sale Securities			(9,022)	(11,027)
Proceeds from sales of available-for-sale securities			2,926	8,546
Proceeds from maturities and repayment of available-for-sale securities			2,002	2,411
Payments to Acquire Held-to-maturity Securities			(709)	(650)
Proceeds from Sale and Maturity of Held-to-maturity Securities			32
Payments to Acquire Loans Held-for-investment			3,090	2,924
Proceeds from Sale of Loans and Leases Held-for-investment			1,227	4,221
Originations and repayments of loans held-for-investment and other			2,718	(6,318)
Purchases of operating lease assets			(2,844)	(2,360)
Disposals of operating lease assets			4,402	4,615
Payments to Acquire Interest in Subsidiaries and Affiliates				0
Proceeds from Contributions from Parent			0	0
Returns of contributed capital			0	0
Increase (Decrease) in Restricted Cash			521	758
Increase (Decrease) in Non marketable equity securities			(20)	(401)
Payments for (Proceeds from) Other Investing Activities			(43)	(103)
Net cash provided by investing activities			(1,387)	(3,273)
Proceeds from (Repayments of) Short-term Debt			(2,255)	(1,745)
Increase (Decrease) in Deposits			12,698	9,276
Proceeds from issuance of long-term debt			10,986	10,145
Repayments of long-term debt			(18,251)	(18,479)
Net Change in Debt, Intercompany			(2,166)	(1,788)
Payments for Repurchase of Redeemable Preferred Stock				0
Payments for Repurchase of Common Stock			0	0
Payments of Dividends			0	0
Dividends paid and returns of contributed capital, Intercompany			(4,459)	(2,968)
Capital contributions from parent			1,200	3,112
Net cash (used in) provided by financing activities			(2,247)	(2,447)
Effect of exchange-rate changes on cash and cash equivalents			3	2
Cash and Cash Equivalents, Period Increase (Decrease)			(612)	(1,936)
Cash and Cash Equivalents, at Carrying Value			5,515	5,595
Cash and Cash Equivalents, at Carrying Value	4,903	3,659	4,903	3,659
Affiliated Entity [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Payments for (Proceeds from) Investments			0
Payments for (Proceeds from) Loans and Leases			0	0
Affiliated Entity [Member] | Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Payments for (Proceeds from) Investments			(7)
Payments for (Proceeds from) Loans and Leases			2,159	1,788
Affiliated Entity [Member] | Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Payments for (Proceeds from) Investments			0
Payments for (Proceeds from) Loans and Leases			0	0
Affiliated Entity [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Payments for (Proceeds from) Investments			(281)
Payments for (Proceeds from) Loans and Leases			232	(41)
Consolidation, Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	(1,037)	(1,117)	(3,068)	(3,291)
Net Cash Provided by (Used in) Operating Activities			(6,247)	(902)
Payments to Acquire Available-for-sale Securities			0	0
Proceeds from sales of available-for-sale securities			0	0
Proceeds from maturities and repayment of available-for-sale securities			0	0
Payments to Acquire Held-to-maturity Securities			0	0
Proceeds from Sale and Maturity of Held-to-maturity Securities			0
Payments to Acquire Loans Held-for-investment			0	0
Proceeds from Sale of Loans and Leases Held-for-investment			0	0
Originations and repayments of loans held-for-investment and other			(1,956)	0
Purchases of operating lease assets			0	0
Disposals of operating lease assets			0	0
Payments to Acquire Interest in Subsidiaries and Affiliates				0
Proceeds from Contributions from Parent			1,200	3,112
Returns of contributed capital			(1,031)	(2,176)
Increase (Decrease) in Restricted Cash			(5)
Increase (Decrease) in Non marketable equity securities			0	0
Payments for (Proceeds from) Other Investing Activities			(91)	102
Net cash provided by investing activities			(4,562)	(709)
Proceeds from (Repayments of) Short-term Debt			0	0
Increase (Decrease) in Deposits			(1,495)	0
Proceeds from issuance of long-term debt			1,961	0
Repayments of long-term debt			0	0
Net Change in Debt, Intercompany			2,532	1,818
Payments for Repurchase of Redeemable Preferred Stock				0
Payments for Repurchase of Common Stock			0	0
Payments of Dividends			0	0
Dividends paid and returns of contributed capital, Intercompany			7,359	2,976
Capital contributions from parent			(1,200)	(3,112)
Net cash (used in) provided by financing activities			9,157	1,682
Effect of exchange-rate changes on cash and cash equivalents			0	0
Cash and Cash Equivalents, Period Increase (Decrease)			(1,652)	71
Cash and Cash Equivalents, at Carrying Value			(401)	(850)
Cash and Cash Equivalents, at Carrying Value	$ (2,053)	$ (779)	(2,053)	(779)
Consolidation, Eliminations [Member] | Affiliated Entity [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Payments for (Proceeds from) Investments			288
Payments for (Proceeds from) Loans and Leases			$ (2,391)	$ (1,747)

Subsequent Events (Details)

Subsequent Events (Details) - $ / shares	Oct. 10, 2017	Sep. 30, 2017
Subsequent Events [Abstract]
Dividends Payable, Amount Per Share	$ 0.12	$ 0.12