Ally Financial (ALLY) 10-Q 1 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	6 Months Ended
	Jun. 30, 2018	Jul. 30, 2018	Jun. 30, 2017
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	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		422,080,891
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 9,452,901,086

Condensed Consolidated Statemen

Condensed Consolidated Statement of Comprehensive Income Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Revenue and Other Income [Line Items]
Interest and Fee Income, Loans and Leases	$ 1,647	$ 1,447	$ 3,190	$ 2,815
Interest and Fee Income, Loans and Leases Held-for-sale	6	0	6	0
Interest and Dividend Income, Securities, Operating, Available-for-sale	188	146	364	280
Interest Income, Deposits with Financial Institutions	17	7	32	12
Operating Leases, Income Statement, Lease Revenue	374	488	756	1,031
Total financing revenue and other interest income	2,232	2,088	4,348	4,138
Interest Expense [Abstract]
Interest Expense, Deposits	399	250	750	481
Interest Expense, Short-term Borrowings	40	33	72	60
Interest Expense, Long-term Debt	434	417	845	841
Interest Expense	873	700	1,667	1,382
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	265	321	538	710
Net Financing Revenue	1,094	1,067	2,143	2,046
Other revenue [Abstract]
Insurance Services Revenue	239	227	495	468
Gain (Loss) on Sales of Loans, Net	1	36	2	50
Gain (Loss) on Investments	27	23	15	50
Noninterest Income, Other Operating Income	97	102	206	216
Nonoperating Income (Expense)	364	388	718	784
Revenues	1,458	1,455	2,861	2,830
Provision for Loan Losses Expensed	158	269	419	540
Noninterest Expense [Abstract]
Labor and Related Expense	292	265	598	550
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	101	125	164	213
Other Noninterest Expense	446	420	891	825
Noninterest Expense	839	810	1,653	1,588
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	461	376	789	702
Income Tax Expense (Benefit)	113	122	189	235
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	348	254	600	467
Net Income (Loss) Attributable to Parent	349	252	599	466
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(70)	76	(398)	96
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	279	328	201	562
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ 1	$ (2)	$ (1)	$ (1)
Earnings Per Share, Basic [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.81	$ 0.55	$ 1.38	$ 1.01
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	(0.01)	0	0
Earnings Per Share, Basic	0.81	0.55	1.38	1.01
Earnings Per Share, Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Diluted Share	0.80	0.55	1.38	1.01
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	(0.01)	0	0
Earnings Per Share, Diluted	0.81	0.55	1.37	1.01
Common Stock, Dividends, Per Share, Declared	$ 0.13	$ 0.08	$ 0.26	$ 0.16
Retained Earnings [Member]
Net Income (Loss) Attributable to Parent	$ 349	$ 252	$ 599	$ 466

Condensed Consolidated Balance

Condensed Consolidated Balance Sheet & Mini Balance Sheet - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Assets [Abstract]
Cash and Due from Banks	$ 799	$ 844
Interest-bearing Deposits in Banks and Other Financial Institutions	3,125	3,408
Cash and Cash Equivalents, at Carrying Value	3,924	4,252
Marketable Securities, Equity Securities	521	518
Available-for-sale securities	23,296	22,303
Held-to-maturity securities	2,089	1,899
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	328	108
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Net of Deferred Income	125,544	122,893
Financing Receivable, Allowance for Credit Losses	1,257	1,276
Loans and Leases Receivable, Net Amount	124,287	121,617
Property Subject to or Available for Operating Lease, Net	8,639	8,741
Premiums receivable and other insurance assets	2,247	2,047
Other Assets	6,014	5,663
Assets	171,345	167,148
Liabilities and Equity [Abstract]
Noninterest-bearing deposit liabilities	153	108
Interest-bearing Deposit Liabilities	98,581	93,148
Deposits	98,734	93,256
Short-term Debt	7,108	11,413
Long-term Debt	47,328	44,226
Interest payable	568	375
Unearned Premiums	2,957	2,604
Accounts Payable and Accrued Liabilities	1,511	1,780
Liabilities	158,206	153,654
Equity [Abstract]
Common Stocks, Including Additional Paid in Capital, Net of Discount	21,303	21,245
Retained Earnings (Accumulated Deficit)	(6,026)	(6,406)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(648)	(235)
Treasury stock, Value	(1,490)	(1,110)
Stockholders' Equity Attributable to Parent, Total	13,139	13,494
Liabilities and Equity	171,345	167,148
Variable Interest Entity, Primary Beneficiary [Member]
Finance receivables and loans, net [Abstract]
Loans and Leases Receivable, Net of Deferred Income	19,386	20,623
Financing Receivable, Allowance for Credit Losses	146	136
Loans and Leases Receivable, Net Amount	19,240	20,487
Property Subject to or Available for Operating Lease, Net	257	444
Other Assets	722	689
Assets	20,219	21,620
Liabilities and Equity [Abstract]
Long-term Debt	12,345	10,197
Accounts Payable and Accrued Liabilities	12	9
Liabilities	$ 12,357	$ 10,206

Consolidated Balance Sheet and

Consolidated Balance Sheet and Mini Balance Sheet (Paranthetical) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
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	492,334,686	489,883,553
Common Stock, Shares, Outstanding		437,053,936
Treasury Stock, Shares	66,582,505	52,829,617
Held-to-maturity Securities, Fair Value	$ 2,007	$ 1,865
End of Period [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Common Stock, Shares, Outstanding	425,752,000	437,054,000

Condensed Consolidated Stateme5

Condensed Consolidated Statement of Changes in Equity - USD ($)	Total	Common stock and paid-in capital [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	$ (341,000,000)			$ (341,000,000)
Stockholders' Equity Attributable to Parent, Total	13,317,000,000	$ 21,166,000,000	$ (7,151,000,000)		$ (357,000,000)
Dividends, Common Stock	0.16
Net Income (Loss) Attributable to Parent	466,000,000		466,000,000
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	42,000,000	42,000,000
Other Comprehensive Income (Loss), Net of Tax	96,000,000			96,000,000
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	96,000,000
Treasury Stock, Value, Acquired, Cost Method	(373,000,000)				(373,000,000)
Dividends, Common Stock, Cash	(75,000,000)		(75,000,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(245,000,000)			(245,000,000)
Stockholders' Equity Attributable to Parent, Total	13,473,000,000	21,208,000,000	(6,760,000,000)		(730,000,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(235,000,000)			(235,000,000)
Stockholders' Equity Attributable to Parent, Total	13,494,000,000	21,245,000,000	(6,406,000,000)		(1,110,000,000)
Dividends, Common Stock	0.26
Net Income (Loss) Attributable to Parent	599,000,000		599,000,000
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	58,000,000	58,000,000
Other Comprehensive Income (Loss), Net of Tax	(398,000,000)			(398,000,000)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(398,000,000)
Treasury Stock, Value, Acquired, Cost Method	(380,000,000)				(380,000,000)
Dividends, Common Stock, Cash	(115,000,000)		(115,000,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(648,000,000)			$ (648,000,000)
Stockholders' Equity Attributable to Parent, Total	13,139,000,000	$ 21,303,000,000	$ (6,026,000,000)		$ (1,490,000,000)
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2014-09 [Member]	(126,000,000)
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01 [Member]	(20,000,000)
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2018-02 [Member]	$ 42,000,000

Condensed Consolidated Stateme6

Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Income (Loss) Attributable to Parent	$ 599	$ 466
Depreciation, Amortization and Accretion, Net	865	1,003
Provision for Loan Losses Expensed Including Discontinued Operations	419	540
Gain Loss on Sales of Loans Net Including Discontinued Operations	(2)	(50)
Availableforsale Securities Gross Realized Gain Loss Excluding Otti Including Disc Ops	(15)	(50)
Payments for Origination and Purchases of Loans Held-for-sale	(730)	(202)
Proceeds from Sale of Loans Held-for-sale	512	187
Increase (Decrease) in Deferred Income Taxes	192	203
Increase (Decrease) in Interest Payable, Net	193	48
Increase (Decrease) in Other Operating Assets	(25)	(94)
Increase (Decrease) in Other Operating Liabilities	(24)	(50)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	25	69
Net Cash Provided by (Used in) Operating Activities	2,009	2,070
Net Cash (Used in) Provided by Investing Activities [Abstract]
Purchases of Equity Securities	(500)	(363)
Proceeds from Sales of Equity Securities	535	484
Payments to Acquire Available-for-sale Securities	(4,094)	(5,490)
Proceeds from Sale of Available-for-sale Securities	390	1,678
Proceeds from maturities and repayment of available-for-sale securities	1,621	1,230
Payments to Acquire Held-to-maturity Securities	(316)	(313)
Proceeds from Sale and Maturity of Held-to-maturity Securities	72	17
Payments for (Proceeds from) Loans and Leases	(2,611)	(1,817)
Proceeds from Sale of Loans Held-for-investment	0	1,280
Originations and repayments of loans held-for-investment and other	(638)	(1,588)
Purchases of operating lease assets	(2,107)	(1,965)
Disposals of Operating Lease Assets	1,763	3,043
Increase (Decrease) in Non marketable equity securities	(46)	107
Payments for (Proceeds from) Other Investing Activities	(186)	(90)
Net cash provided by investing activities	(6,117)	(3,787)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Proceeds from (Repayments of) Short-term Debt	(4,305)	(1,962)
Increase (Decrease) in Deposits	5,441	7,133
Proceeds from Issuance of Long-term Debt	12,940	9,330
Repayments of long-term debt	(9,800)	(14,366)
Payments for Repurchase of Common Stock	(380)	(373)
Payments of Dividends	(115)	(75)
Net cash (used in) provided by financing activities	3,781	(313)
Effect of Exchange Rate on Cash and Cash Equivalents	(3)	2
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(330)	(2,028)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	4,939	5,853
Cash and Cash Equivalents, at Carrying Value	3,924	4,377
Restricted Cash	1,015	1,476
Supplemental Cash Flow Information [Abstract]
Interest Paid	1,455	1,331
Income Taxes Paid	17	28
Held-to-maturity securities received in consideration for loans sold	0	56
Transfer of Portfolio Loans and Leases to Held-for-sale	0	1,298
Proceeds from sales and repayments of mortgage loans held-for-investment originally designated as held-for-sale	$ 12	$ 20

Description of Business, Basis

Description of Business, Basis of Presentation, and Changes in Significant Accounting Policies	6 Months Ended
	Jun. 30, 2018
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) based on total assets, offering diversified financial products and services for consumers, businesses, automotive dealers, and corporate clients. Ally operates with a distinctive brand, an innovative approach, and a relentless focus on our customers. We are a Delaware corporation 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 legacy that dates back to 1919, 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 banking preferences for digital banking . We offer mortgage lending services and a variety of deposit and other banking products, including CDs, online savings, money market and checking accounts, and IRA products. We also promote a cash back credit card. 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 primarily offer senior secured leveraged cash flow and asset-based loans 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 June 30, 2018 , and for the three months and six months ended June 30, 2018 , and 2017 , 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, 2017 , as filed on February 21, 2018, with the U.S. Securities and Exchange Commission (SEC). Significant Accounting Policies Investments Our investment portfolio includes various debt and equity securities. Our debt securities include government securities, corporate bonds, asset-backed securities (ABS), and mortgage-backed securities (MBS). Debt securities are classified based on management’s intent to sell or hold the security. We classify debt securities as held-to-maturity only when we have both the intent and ability to hold the securities to maturity. We classify debt securities as trading when the securities are acquired for the purpose of selling or holding them for a short period of time. Debt securities not classified as either held-to-maturity or trading are classified as available-for-sale. Our portfolio includes debt securities classified as available-for-sale and held-to-maturity. Our available-for-sale debt securities are carried at fair value with unrealized gains and losses included in accumulated other comprehensive loss and are subject to impairment. Our held-to-maturity debt securities are carried at amortized cost and are subject to impairment. We assess our available-for-sale and held-to-maturity debt securities for potential other-than-temporary impairment. We employ a methodology that considers available evidence in evaluating potential other-than-temporary impairment of our debt securities. If the cost of an investment exceeds its fair value, we evaluate, among other factors, the magnitude and duration of the decline in fair value. We also evaluate the financial health of and business outlook for the issuer, the performance of the underlying assets for interests in securitized assets, and, for debt securities classified as available-for-sale, our intent and ability to hold the investment through recovery of its amortized cost basis. Once a decline in fair value of a debt security is determined to be other-than-temporary, an impairment charge for the credit component is recorded to other gain (loss) on investments, net, in our Condensed Consolidated Statement of Comprehensive Income, and a new cost basis in the investment is established. The noncredit loss component of an available-for-sale debt security continues to be recorded in other comprehensive (loss) income when we do not intend to sell the security and it is not more likely than not that we will have to sell the security prior to the security’s anticipated recovery. Both the credit and noncredit loss components are recorded in earnings when we intend to sell the security or it is more likely than not that we will have to sell the security prior to the security’s anticipated recovery. Subsequent increases and decreases to the fair value of available-for-sale debt securities are included in other comprehensive (loss) income, so long as they are not attributable to another other-than-temporary impairment. We amortize premiums and discounts on debt securities as an adjustment to investment yield generally over the stated maturity of the security. For ABS and MBS where prepayments can be reasonably estimated, amortization is adjusted for expected prepayments. Our investment in equity securities includes securities that are recognized at fair value with changes in the fair value recorded in earnings, and equity securities that are recognized using other measurement principles. Effective January 1, 2018, equity securities that have a readily determinable fair value, as well as certain investments that do not have a readily determinable fair value and are not eligible to be recognized using other measurement principles, are recorded at fair value with changes in fair value recorded in earnings and reported in other gain (loss) on investments, net in our Condensed Consolidated Statement of Comprehensive Income . These investments, which are primarily attributable to the investment portfolio of our Insurance operations, are included in equity securities on our Condensed Consolidated Balance Sheet . Refer to Note 6 for further information on our equity securities that have a readily determinable market value. Our equity securities recognized using other measurement principles include investments in Federal Home Loan Bank (FHLB) and Federal Reserve Bank (FRB) stock held to meet regulatory requirements, equity investments related to low income housing tax credits and the Community Reinvestment Act (CRA), which do not have a readily determinable fair value, and other equity investments that do not have a readily determinable fair value. Our low income housing tax credit investments are accounted for using the proportional amortization method of accounting for qualified affordable housing investments. Our obligations related to unfunded commitments for our low income housing tax credit investments are included in other liabilities. The majority of our CRA investments are accounted for using the equity method of accounting. Our investments in low income housing tax credits and CRA investments are included in other assets on our Condensed Consolidated Balance Sheet. Our investments in FHLB and FRB stock are carried at cost. Our remaining investments in equity securities are recorded at cost, less impairment and adjusted for observable price changes under the measurement alternative provided under GAAP. These investments, along with our investments in FHLB and FRB stock, are included in nonmarketable equity investments in other assets on our Condensed Consolidated Balance Sheet. As conditions warrant, we review these investments for impairment and adjust the carrying value of the investment if it is deemed to be impaired. Investments recorded under the measurement alternative are also reviewed at each reporting period to determine if any adjustments are required for observable price changes in identical or similar securities of the same issuer. Realized gains and losses on the sale of securities are determined using the specific identification method and are reported in other gain (loss) on investments, net in our Condensed Consolidated Statement of Comprehensive Income. Derivative Instruments and Hedging Activities We use derivative instruments primarily for risk management purposes. We do not use derivative instruments for speculative purposes. Certain of our derivative instruments are designated as accounting hedges in qualifying relationships, whereas other derivative instruments have not been designated as accounting hedges. In accordance with applicable accounting standards, all derivative instruments, whether designated for hedge accounting or not, are required to be recorded on the balance sheet as assets or liabilities and measured at fair value. We have elected to report the fair value of derivative assets and liabilities on a gross basis—including the fair value for the right to reclaim cash collateral or the obligation to return cash collateral—arising from instruments executed with the same counterparty under a master netting arrangement where we do not have the intent to offset. For additional information on derivative instruments and hedging activities, refer to Note 18 . At the inception of a hedge accounting relationship, we designate each qualifying hedge relationship as a hedge of the fair value of a specifically identified asset or liability (fair value hedge); as a hedge of the variability of cash flows to be received or paid, or forecasted to be received or paid, related to a recognized asset or liability (cash flow hedge); or as a hedge of the foreign-currency exposure of a net investment in a foreign operation (net investment hedge). We formally document all relationships between hedging instruments and hedged items, as well as the risk management objectives for undertaking various hedge transactions. Both at hedge inception and on an ongoing basis, we formally assess whether the derivatives that are used in hedging relationships are highly effective in offsetting changes in the fair values or cash flows of hedged items. Changes in the fair value of derivative instruments qualifying as fair value hedges, along with the gain or loss on the hedged asset or liability attributable to the hedged risk, are recorded in current period earnings. For qualifying cash flow hedges, the changes in fair value of the derivative financial instruments are recorded in accumulated other comprehensive loss and recognized in the income statement when the hedged cash flows affect earnings. For a qualifying net investment hedge, the gain or loss is reported in accumulated other comprehensive loss as part of the cumulative translation adjustment. Hedge accounting treatment is no longer applied if a derivative financial instrument is terminated, or if the hedge designation is removed or assessed to be no longer highly effective. For terminated fair value hedges, any changes to the hedged asset or liability remain as part of the basis of the hedged asset or liability and are recognized into income over the remaining life of the asset or liability. For terminated cash flow hedges, unless it is probable that the forecasted cash flows will not occur within a specified period, any changes in fair value of the derivative financial instrument previously recognized remain in accumulated other comprehensive loss, and are reclassified into earnings in the same period that the hedged cash flows affect earnings. Any previously recognized gain or loss for a net investment hedge continues to remain in accumulated other comprehensive loss until earnings are impacted by sale or liquidation of the associated foreign operation. In all instances, after hedge accounting is no longer applied, any subsequent changes in fair value of the derivative instrument will be recorded into earnings. Changes in the fair value of derivative financial instruments held for risk management purposes that are not designated as accounting hedges under GAAP are reported in current period earnings. 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 2017 Annual Report on Form 10-K, which describes our annual significant income tax accounting policy and related methodology. Refer to Note 1 to the Consolidated Financial Statements in our 2017 Annual Report on Form 10-K regarding additional significant accounting policies. Recently Adopted Accounting Standards Statement of Cash Flows — Restricted Cash (ASU 2016-18) As of December 31, 2017, we elected to early-adopt Accounting Standards Update (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. The amendments were applied retrospectively to all periods presented within the statement of cash flows. The implementation of this guidance resulted in a change in presentation of our Condensed Consolidated Statement of Cash Flows and additional disclosures surrounding restricted cash balances, but did not result in a change to our Condensed Consolidated Statement of Comprehensive Income or Condensed Consolidated Balance Sheet. Revenue from Contracts with Customers (ASU 2014-09) 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. 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. The FASB issued several additional ASUs to clarify guidance and provide implementation support for ASU 2014-09. The clarifying guidance elaborates on the key concepts within ASU 2014-09 and clarifies how those concepts interact with other GAAP requirements. On January 1, 2018, we adopted ASU 2014-09 and all subsequent ASUs that modified ASU 2014-09 (collectively, the amendments to the revenue recognition principles), which have been codified in ASC 606, Revenue from Contracts with Customers, and ASC 610-20, Gains and Losses from the Derecognition of Nonfinancial Assets , respectively. We elected to adopt this guidance using the modified retrospective approach applied to all contracts with customers that were not completed as of January 1, 2018. The adoption of the amendments resulted in a reduction to our opening retained earnings of approximately $126 million , net of income taxes. Refer to Note 2 for further details. Financial Instruments — Recognition and Measurement of Financial Assets (ASU 2016-01) As of January 1, 2018, we adopted 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. The FASB subsequently issued ASU 2018-03 to clarify guidance and provide implementation support for ASU 2016-01, which we elected to early-adopt as of January 1, 2018, to align with the adoption of ASU 2016-01. 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 are no longer recognized through other comprehensive (loss) income , which creates additional volatility in our Condensed Consolidated Statement of Comprehensive Income. Reporting entities may continue to elect to measure certain 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 (loss) income and not as a component of net income. We adopted these amendments, as required, on a modified retrospective basis with a cumulative effect adjustment as of the beginning of the fiscal year of initial adoption. The adoption of the amendments resulted in a reduction to our opening retained earnings of approximately $20 million , net of income taxes. Derivatives and Hedging — Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12) As of January 1, 2018, we elected to early-adopt ASU 2017-12. The amendments in this update enhance the financial reporting of hedging relationships to better align hedge accounting with an entity’s risk management activities. This update also makes certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP and better portrays economic results through changes to both the designation and measurement guidance for qualifying hedging relationships and presentation of hedge results. We adopted the amendments to all cash flow and net investment hedge relationships that existed on the date of adoption using a modified retrospective approach. No cumulative effect adjustment to our opening retained earnings was required as a result of the adoption. The presentation and disclosure requirements included in this update were adopted prospectively. Refer to Note 18 for further details. Accumulated Other Comprehensive Income — Reclassification of Certain Tax Effects (ASU 2018-02) In February 2018, the FASB issued ASU 2018-02. The amendments in this update provide guidance concerning the treatment of the impact of income tax effects resulting from the Tax Cuts and Jobs Act of 2017 (the Tax Act) on items included in accumulated other comprehensive income. Our policy is to use the portfolio method with respect to reclassification of stranded income tax effects in accumulated other comprehensive loss. The amendments in ASU 2018-02 provide entities an election to reclassify the income tax effect of the Tax Act from accumulated other comprehensive income to retained earnings. We elected to early-adopt this standard as of January 1, 2018, and reclassified the effect of the change in the federal corporate income tax rate on items included in accumulated other comprehensive loss. This election resulted in a reclassification of $42 million from accumulated other comprehensive loss to retained earnings. Recently Issued Accounting Standards 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. We are currently in the process of reviewing our lease contracts and examining the practical expedients and accounting policy elections provided in the amendments, as well as ensuring our control environment and reporting processes reflect the requirements of the amendments. Upon adoption, our balance sheet will include a right-of-use asset and lease liability for our operating leases where we are the lessee, which primarily include our facilities leases. In addition, we will no longer capitalize certain initial direct costs in connection with lease originations where we are the lessor. We do not anticipate the adoption of these amendments will have a material impact to our financial statements. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as currently 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 recorded under the current incurred loss model 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. The amount of the change in the allowance for credit losses will also be impacted by the composition of our portfolio at the adoption date, as well as economic conditions and forecasts at that time. Management created a cross-functional working group to govern the implementation of these amendments, including consideration of model development, data integrity, technology, reporting and disclosure requirements, key accounting interpretations, control environment, and corporate governance. 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. 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. While our assessment is not final, we do not expect the amendments to have a material impact to our financial statements and are currently in the process of ensuring our control environment and reporting processes reflect the requirements of the amendments. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as required.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Text Block]	Revenue from Contracts with Customers On January 1, 2018, we adopted the amendments to the revenue recognition principles using the modified retrospective approach applied to contracts with customers outstanding as of the date of adoption. Results for reporting periods beginning after January 1, 2018, are presented in accordance with the amendments to the revenue recognition principles, while prior period amounts have not been adjusted and continue to be presented in accordance with the accounting standards in effect for those periods. Refer to Note 1 for additional information. Our primary revenue sources, which include financing revenue and other interest income, are addressed by other GAAP and are not in the scope of the amendments to the revenue recognition principles. As part of our Insurance operations, we recognize revenue from insurance contracts, which are addressed by other GAAP and are not included in the scope of the amendments to the revenue recognition principles. Certain noninsurance contracts within our Insurance operations, including vehicle service contracts (VSCs), guaranteed asset protection (GAP) contracts, and vehicle maintenance contracts (VMCs), are included in the scope of the amendments to the revenue recognition principles. Under the previous guidance, a portion of revenue earned on noninsurance contracts was recognized at contract inception, while the remainder was recognized over the contract term on a basis proportionate to the anticipated cost emergence. In addition, dealer and sales commissions incurred to obtain a noninsurance contract were recognized as expense when incurred, and certain direct-response advertising costs were deferred and recognized as expense over the term of the contract. Upon adoption of the amendments to the revenue recognition principles, all revenue associated with noninsurance contracts is recognized over the contract term on a basis proportionate to the anticipated cost emergence. Further, commissions and sales expense incurred to obtain these contracts are capitalized and recognized as expense over the contract term, and all advertising costs are recognized as expense when incurred. The following table presents the impact to our Condensed Consolidated Balance Sheet as of January 1, 2018, as a result of adopting the amendments to the revenue recognition principles. ($ in millions) As reported, December 31, 2017 Adjustment related to adoption As adjusted, January 1, 2018 Assets Premiums receivable and other insurance assets $ 2,047 $ 122 $ 2,169 Other assets 5,663 41 5,704 Total assets $ 167,148 $ 163 $ 167,311 Liabilities Unearned insurance premiums and service revenue $ 2,604 $ 289 $ 2,893 Total liabilities 153,654 289 153,943 Equity Accumulated deficit (6,406 ) (126 ) (6,532 ) Total equity 13,494 (126 ) 13,368 Total liabilities and equity $ 167,148 $ 163 $ 167,311 The following tables present the impact of adopting the amendments to the revenue recognition principles to our Condensed Consolidated Statement of Comprehensive Income and Condensed Consolidated Balance Sheet . Three months ended June 30, 2018 Six months ended June 30, 2018 ($ in millions) As reported Effect of adoption As reported Effect of adoption Other revenue Insurance premiums and service revenue earned $ 239 $ (9 ) $ 495 $ (15 ) Total other revenue 364 (9 ) 718 (15 ) Total net revenue 1,458 (9 ) 2,861 (15 ) Noninterest expense Compensation and benefits expense 292 (1 ) 598 (2 ) Other operating expenses 446 (3 ) 891 (5 ) Total noninterest expense 839 (4 ) 1,653 (7 ) Income from continuing operations before income tax expense 461 (5 ) 789 (8 ) Income tax expense from continuing operations 113 (1 ) 189 (2 ) Net income from continuing operations 348 (4 ) 600 (6 ) Net income 349 (4 ) 599 (6 ) Comprehensive income $ 279 $ (4 ) $ 201 $ (6 ) June 30, 2018 ($ in millions) As reported Effect of adoption Assets Premiums receivable and other insurance assets $ 2,247 $ 128 Other assets 6,014 43 Total assets 171,345 171 Liabilities Unearned insurance premiums and service revenue $ 2,957 $ 304 Total liabilities 158,206 304 Equity Accumulated deficit (6,026 ) (133 ) Total equity 13,139 (133 ) Total liabilities and equity $ 171,345 $ 171 The following is a description of our primary revenue sources that are derived from contracts with customers. As a result of the adoption of the amendments to the revenue recognition principles, our only revenue source for which the recognition pattern was affected was that of noninsurance contracts, as described in this note. Revenue from contracts with customers is recognized when control of the promised goods or services is transferred to our customers, and in an amount that reflects the consideration that we expect to receive in exchange for those goods or services. For information regarding our revenue recognition policies outside the scope of the amendments to the revenue recognition principles of ASC 606, Revenue from Contracts with Customers , refer to Note 1 to the Consolidated Financial Statements in our 2017 Annual Report on Form 10-K. • Noninsurance contracts — We sell VSCs that offer owners mechanical repair protection and roadside assistance for new and used vehicles beyond the manufacturer’s new vehicle limited warranty. We sell GAP contracts that protect the customer against having to pay certain amounts to a lender above the fair market value of their vehicle if the vehicle is damaged and declared a total loss or stolen. We also sell VMCs that provide coverage for certain agreed-upon services, such as oil changes and tire rotations, over the coverage period. We receive payment in full at the inception of each of these contracts. Our performance obligation for these contracts is satisfied over the term of the contract and we recognize revenue over the contract term on a basis proportionate to the anticipated cost emergence, as we believe this is the most appropriate method to measure progress towards satisfaction of the performance obligation. Upon adoption of the amendments to the revenue recognition principles, unearned revenue of $289 million was recognized as a component of unearned insurance premiums and service revenue on our Condensed Consolidated Balance Sheet associated with outstanding contracts at January 1, 2018, and $22 million and $44 million of this balance were recognized as insurance premiums and service revenue earned in our Condensed Consolidated Statement of Comprehensive Income during the three months and six months ended June 30, 2018 , respectively. At June 30, 2018 , we had unearned revenue of $2.6 billion associated with outstanding contracts, and with respect to this balance we expect to recognize revenue of $407 million during the remainder of 2018 , $663 million in 2019 , $564 million in 2020 , $423 million in 2021 , and $501 million thereafter. The incremental costs to obtain these contracts are initially deferred and recorded as a component of premiums receivable and other insurance assets on our Condensed Consolidated Balance Sheet . These deferred costs are amortized as an expense over the term of the related contract commensurate with how the related revenue is recognized, and are included in compensation and benefits and other operating expenses in our Condensed Consolidated Statement of Comprehensive Income . We had deferred insurance assets of $1.5 billion at June 30, 2018 , and recognized $106 million and $209 million of expense during the three months and six months ended June 30, 2018 , respectively. • Sale of off-lease vehicles — When a customer’s vehicle lease matures, the customer has the option of purchasing or returning the vehicle. If the vehicle is returned to us, we obtain possession with the intent to sell through SmartAuction—our online auction platform, our dealer channel, or through various other physical auctions. Our performance obligation is satisfied and the remarketing gain or loss is recognized when control of the vehicle has passed to the buyer, which coincides with the sale date. Our actual sales proceeds from remarketing the vehicle may be higher or lower than the estimated residual value resulting in a gain or loss on remarketing recorded through depreciation expense on operating lease assets in our Condensed Consolidated Statement of Comprehensive Income . • Remarketing fee income — In addition to using SmartAuction as a remarketing channel for our returned lease vehicles, we maintain the internet auction site and administer the auction process for third-party use. We earn a service fee from dealers for every third-party vehicle sold through SmartAuction. Our performance obligation is to provide the online marketplace for used vehicle transactions to be consummated. This obligation is satisfied and revenue is recognized when control of the vehicle has passed to the buyer, which coincides with the sale date. This revenue is recorded as remarketing fees within other income in our Condensed Consolidated Statement of Comprehensive Income . • Brokerage commissions and other revenues through Ally Invest — We charge fees to customers related to their use of certain services on our Ally Invest digital wealth management and online brokerage platform. These fees include commissions on customer-directed trades, account service fees, account management fees on professional portfolio management services, subscriptions for market data feeds, and other ancillary fees. Commissions on customer-directed trades and account service fees are based on published fee schedules and are generated from a customer option to purchase the services offered under the contract. These options do not represent a material right and are only considered a contract when the customer executes their option to purchase these services. Based on this, the term of the contract does not extend beyond services provided, and as such revenue is recognized upon the completion of our performance obligation, which we view as the successful execution of the trade or service. Revenue on professional portfolio management services is calculated monthly based upon a fixed percentage of the client’s assets under management. Due to the fact that this revenue stream is composed of variable consideration that is based on factors outside of our control, we have deemed this revenue as constrained and we are unable to estimate the initial transaction price at the inception of the contract. We have elected to use the practical expedient under GAAP to recognize revenue monthly based on the amount we are able to invoice the customer. Subscriptions for market data feeds are based on published fee schedules, and our performance obligation for these contracts is satisfied over the term of the contract, which does not exceed 12 months. We receive payment in full at contract inception and recognize revenue over the related contract term on a straight-line basis, as we believe this is the most appropriate method to measure progress towards satisfaction of the performance obligation. We also earn revenue from a fee-sharing agreement with our clearing broker related to the interest income the clearing broker earns on customer cash balances and margin loans made to our customers. Ally concluded the initial transaction price is exclusively variable consideration and, based on the nature of our performance obligation to allow the clearing broker to collect interest income from cash deposits and customer loans from our customers, we are unable to determine the amount of revenue to be recognized until the total customer cash balance or the total interest income recognized on margin loans has been determined, which occurs monthly. These revenue streams are recorded as other income in our Condensed Consolidated Statement of Comprehensive Income . • Brokered/agent commissions through Insurance operations — We have agreements with third parties to offer various vehicle protection products to consumers. We also have agreements with third-party insurers to offer various insurance coverages to dealers. Our performance obligation for these arrangements is satisfied when a customer or dealer has purchased a vehicle protection product or an insurance policy through the third-party provider. In determining the initial transaction price for these agreements, we noted that revenue on brokered/agent commissions is based on the volume of vehicle protection product contracts sold or a percentage of insurance premium written, which is not known to Ally at the inception of the agreements with these third-party providers. As such, we believe the initial transaction price is exclusively variable consideration and, based on the nature of the performance obligation, we are unable to determine the amount of revenue we will record until the customer purchases a vehicle protection product or a dealer purchases an insurance policy from the third-party provider. Once Ally is notified of vehicle protection product sales or insurance policies issued by the third-party providers, we record the commission earned as insurance premiums and service revenues earned in our Condensed Consolidated Statement of Comprehensive Income . • Deposit account and other banking fees — We charge depositors various account service fees including those for outgoing wires, excessive transactions, overdrafts, stop payments, and returned deposits. These fees are generated from a customer option to purchase services offered under the contract. These options do not represent a material right and are only considered a contract in accordance with the amendments to the revenue recognition principles when the customer exercises their option to purchase these account services. Based on this, the term for our contracts with customers is considered day-to-day, and the contract does not extend beyond the services already provided. Revenue derived from deposit account fees is recorded at the point in time we perform the requested service, and is recorded as other income in our Condensed Consolidated Statement of Comprehensive Income . As a debit card issuer, we also generate interchange fee income from merchants during debit card transactions and incur certain corresponding charges from merchant card networks. Our performance obligation is satisfied when we have initiated the payment of funds from a customer’s account to a merchant through our contractual agreements with the merchant card networks. Interchange fees are reported on a net basis as other income in our Condensed Consolidated Statement of Comprehensive Income . Gross interchange fee income was $3 million and $6 million , and interchange expense was $2 million and $5 million , for the three months and six months ended June 30, 2018 , respectively. • Other revenue — Other revenue primarily includes service revenue related to various account management functions, fee income derived from third-party loans arranged through Clearlane—our online automotive lender exchange, and revenue associated with licensing and marketing from the Ally CashBack Credit Card—our co-branded credit card. These revenue streams are recorded as other income in our Condensed Consolidated Statement of Comprehensive Income . The following table presents a disaggregated view of our revenue from contracts with customers included in other revenue that falls within the scope of the amendments to the revenue recognition principles. Three months ended June 30, 2018 ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated Revenue from contracts with customers Noninsurance contracts $ — $ 125 $ — $ — $ — $ 125 Remarketing fee income 21 — — — — 21 Brokerage commissions and other revenue — — — — 15 15 Brokered/agent commissions — 4 — — — 4 Deposit account and other banking fees — — — — 3 3 Other 4 — — — — 4 Total revenue from contracts with customers 25 129 — — 18 172 All other revenue 38 137 2 14 1 192 Total other revenue (a) $ 63 $ 266 $ 2 $ 14 $ 19 $ 364 (a) Represents a component of total net revenue. Refer to Note 22 for further information on our reportable operating segments. Six months ended June 30, 2018 ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated Revenue from contracts with customers Noninsurance contracts $ — $ 248 $ — $ — $ — $ 248 Remarketing fee income 44 — — — — 44 Brokerage commissions and other revenue — — — — 31 31 Brokered/agent commissions — 8 — — — 8 Deposit account and other banking fees — — — — 6 6 Other 6 1 — — — 7 Total revenue from contracts with customers 50 257 — — 37 344 All other revenue 79 255 3 22 15 374 Total other revenue (a) $ 129 $ 512 $ 3 $ 22 $ 52 $ 718 (a) Represents a component of total net revenue. Refer to Note 22 for further information on our reportable operating segments. In addition to the components of other revenue presented above, as part of our Automotive Finance operations, we recognized gains of $16 million and $34 million for the three months and six months ended June 30, 2018 , respectively, on the sale of off-lease vehicles. These gains are included in depreciation expense on operating lease assets in our Condensed Consolidated Statement of Comprehensive Income .

Other Income, Net of Losses

Other Income, Net of Losses	6 Months Ended
	Jun. 30, 2018
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 June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Late charges and other administrative fees $ 25 $ 25 $ 54 $ 52 Remarketing fees 21 27 44 56 Servicing fees 8 14 16 30 Income from equity-method investments 7 5 13 5 Other, net 36 31 79 73 Total other income, net of losses $ 97 $ 102 $ 206 $ 216

Reserves for Insurance Losses a

Reserves for Insurance Losses and Loss Adjustment Expenses	6 Months Ended
	Jun. 30, 2018
Reserves for Insurance Losses and Loss Adjustment Expense [Abstract]
Reserves for Insurance Losses and Loss Adjustment Expenses [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) 2018 2017 Total gross reserves for insurance losses and loss adjustment expenses at January 1, $ 140 $ 149 Less: Reinsurance recoverable 108 108 Net reserves for insurance losses and loss adjustment expenses at January 1, 32 41 Net insurance losses and loss adjustment expenses incurred related to: Current year 159 211 Prior years (a) 5 2 Total net insurance losses and loss adjustment expenses incurred 164 213 Net insurance losses and loss adjustment expenses paid or payable related to: Current year (121 ) (183 ) Prior years (26 ) (27 ) Total net insurance losses and loss adjustment expenses paid or payable (147 ) (210 ) Net reserves for insurance losses and loss adjustment expenses at June 30, 49 44 Plus: Reinsurance recoverable 100 135 Total gross reserves for insurance losses and loss adjustment expenses at June 30, $ 149 $ 179 (a) There have been no material adverse changes to the reserve for prior years.

Other Operating Expenses

Other Operating Expenses	6 Months Ended
	Jun. 30, 2018
Operating Expenses [Abstract]
Other Operating Income and Expense [Text Block]	Other Operating Expenses Details of other operating expenses were as follows. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Insurance commissions $ 109 $ 104 $ 219 $ 203 Technology and communications 74 71 145 140 Lease and loan administration 40 39 82 75 Advertising and marketing 29 33 68 63 Professional services 35 27 67 53 Regulatory and licensing fees 35 28 65 55 Vehicle remarketing and repossession 26 25 58 53 Premises and equipment depreciation 22 23 42 45 Occupancy 11 11 22 23 Non-income taxes 6 8 14 16 Amortization of intangible assets 3 3 6 6 Other 56 48 103 93 Total other operating expenses $ 446 $ 420 $ 891 $ 825

Investment Securities

Investment Securities	6 Months Ended
	Jun. 30, 2018
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 available-for-sale and held-to-maturity debt securities includes bonds, asset-backed securities, commercial and residential mortgage-backed securities, and other investments. We also hold equity securities. The cost, fair value, and gross unrealized gains and losses on available-for-sale and held-to-maturity investment securities were as follows. June 30, 2018 December 31, 2017 Amortized cost Gross unrealized Fair value Amortized cost Gross unrealized Fair value ($ in millions) gains losses gains losses Available-for-sale securities Debt securities U.S. Treasury $ 1,963 $ 1 $ (90 ) $ 1,874 $ 1,831 $ — $ (54 ) $ 1,777 U.S. States and political subdivisions 865 5 (19 ) 851 850 11 (7 ) 854 Foreign government 155 1 (2 ) 154 153 2 (1 ) 154 Agency mortgage-backed residential 15,559 4 (497 ) 15,066 14,412 35 (156 ) 14,291 Mortgage-backed residential 2,716 2 (93 ) 2,625 2,517 11 (34 ) 2,494 Mortgage-backed commercial 644 1 (3 ) 642 541 1 (1 ) 541 Asset-backed 870 2 (4 ) 868 933 4 (1 ) 936 Corporate debt 1,258 1 (43 ) 1,216 1,262 5 (11 ) 1,256 Total available-for-sale securities (a) (b) (c) $ 24,030 $ 17 $ (751 ) $ 23,296 $ 22,499 $ 69 $ (265 ) $ 22,303 Held-to-maturity securities Debt securities Agency mortgage-backed residential (d) $ 2,062 $ 1 $ (83 ) $ 1,980 $ 1,863 $ 3 $ (37 ) $ 1,829 Asset-backed retained notes 27 — — 27 36 — — 36 Total held-to-maturity securities $ 2,089 $ 1 $ (83 ) $ 2,007 $ 1,899 $ 3 $ (37 ) $ 1,865 (a) Certain entities related to our Insurance operations are required to deposit securities with state regulatory authorities. These deposited securities totaled $12 million at both June 30, 2018 , and December 31, 2017. (b) Certain available-for-sale securities are included in fair value hedging relationships. Refer to Note 18 for additional information. (c) Investment securities with a fair value of $7.1 billion and $7.8 billion at June 30, 2018 , and December 31, 2017 , respectively, were pledged to secure advances from the 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 $1.2 billion and $1.0 billion of the underlying investment securities at June 30, 2018 , and December 31, 2017 , respectively. (d) Securities with a fair value of $962 million and $664 million at June 30, 2018 , and December 31, 2017, respectively, were pledged to secure advances from the FHLB. The maturity distribution of debt securities outstanding is summarized in the following tables. Call or prepayment options may cause actual maturities to differ from contractual maturities. Total Due in one year or less Due after one year through five years Due after five years through ten years Due after ten years ($ in millions) Amount Yield Amount Yield Amount Yield Amount Yield Amount Yield June 30, 2018 Fair value of available-for-sale securities (a) U.S. Treasury $ 1,874 1.9 % $ 13 1.4 % $ 578 1.9 % $ 1,283 1.8 % $ — — % U.S. States and political subdivisions 851 3.1 35 3.4 53 2.2 237 2.6 526 3.4 Foreign government 154 2.5 25 3.3 61 2.3 68 2.4 — — Agency mortgage-backed residential 15,066 3.2 — — — — 25 2.0 15,041 3.2 Mortgage-backed residential 2,625 3.2 — — — — — — 2,625 3.2 Mortgage-backed commercial 642 3.6 — — — — 31 3.6 611 3.6 Asset-backed 868 3.3 — — 618 3.3 137 3.6 113 3.0 Corporate debt 1,216 3.1 122 2.8 472 2.7 589 3.3 33 4.9 Total available-for-sale securities $ 23,296 3.1 $ 195 2.9 $ 1,782 2.6 $ 2,370 2.4 $ 18,949 3.2 Amortized cost of available-for-sale securities $ 24,030 $ 195 $ 1,811 $ 2,476 $ 19,548 Amortized cost of held-to-maturity securities Agency mortgage-backed residential $ 2,062 3.1 % $ — — % $ — — % $ — — % $ 2,062 3.1 % Asset-backed retained notes 27 1.8 — — 26 1.8 1 3.0 — — Total held-to-maturity securities $ 2,089 3.1 $ — — $ 26 1.8 $ 1 3.0 $ 2,062 3.1 December 31, 2017 Fair value of available-for-sale securities (a) U.S. Treasury $ 1,777 1.7 % $ — — % $ 487 1.7 % $ 1,290 1.8 % $ — — % U.S. States and political subdivisions 854 2.9 76 1.8 36 2.3 203 2.5 539 3.3 Foreign government 154 2.5 — — 80 2.5 74 2.4 — — Agency mortgage-backed residential 14,291 3.1 — — — — 3 2.9 14,288 3.1 Mortgage-backed residential 2,494 3.1 — — — — — — 2,494 3.1 Mortgage-backed commercial 541 3.2 — — 30 3.1 31 3.1 480 3.2 Asset-backed 936 3.1 — — 698 3.1 106 3.1 132 2.8 Corporate debt 1,256 2.9 140 2.6 513 2.6 564 3.2 39 4.7 Total available-for-sale securities $ 22,303 3.0 $ 216 2.3 $ 1,844 2.5 $ 2,271 2.3 $ 17,972 3.1 Amortized cost of available-for-sale securities $ 22,499 $ 217 $ 1,852 $ 2,314 $ 18,116 Amortized cost of held-to-maturity securities Agency mortgage-backed residential $ 1,863 3.1 % $ — — % $ — — % $ — — % $ 1,863 3.1 % Asset-backed retained notes 36 1.7 — — 35 1.7 1 3.0 — — Total held-to-maturity securities $ 1,899 3.1 $ — — $ 35 1.7 $ 1 3.0 $ 1,863 3.1 (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. The balances of cash equivalents were $54 million and $10 million at June 30, 2018 , and December 31, 2017 , respectively, and were composed primarily of money market accounts and short-term securities, including U.S. Treasury bills. The following table presents interest and dividends on investment securities. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Taxable interest $ 164 $ 130 $ 318 $ 249 Taxable dividends 3 3 6 5 Interest and dividends exempt from U.S. federal income tax 6 6 12 11 Interest and dividends on investment securities $ 173 $ 139 $ 336 $ 265 The following table presents gross gains and losses realized upon the sales of available-for-sale securities, and net gains or losses on equity securities held during the period. There were no other-than-temporary impairments of available-for-sale securities for either period. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Available-for-sale securities Gross realized gains $ 1 $ 24 $ 7 $ 51 Gross realized losses (a) — (1 ) — (1 ) Net realized gains on available-for-sale securities 1 23 7 50 Net realized gain on equity securities 18 40 Net unrealized gain (loss) on equity securities (b) 8 (32 ) Other gain on investments, net $ 27 $ 23 $ 15 $ 50 (a) Certain available-for-sale securities were sold at a loss in 2018 and 2017 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. (b) As a result of our adoption of ASU 2016-01, beginning January 1, 2018, changes in the fair value of our portfolio of equity securities are recognized in net income. Prior to adoption, equity securities were included in our available-for-sale portfolio and unrealized changes in fair value were recognized through other comprehensive (loss) income until realized, at which point we recorded a gain or loss on sale. We adopted ASU 2016-01 on January 1, 2018, on a modified retrospective basis with a cumulative effect adjustment as of the beginning of the fiscal year of initial adoption. Refer to the section titled Recently Adopted Accounting Standards in Note 1 for additional information. The table below summarizes available-for-sale and held-to-maturity securities in an unrealized loss position, which we evaluated for other than temporary impairment applying the methodology described in Note 1 . As of June 30, 2018 , we did not have the intent to sell the available-for-sale or held-to-maturity securities with an unrealized loss position and we do not believe it is more likely than not that we will be required to sell these securities before recovery of their amortized cost basis. As a result of this evaluation, we believe that the securities with an unrealized loss position are not considered to be other-than-temporarily impaired at June 30, 2018 . June 30, 2018 December 31, 2017 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 $ 485 $ (19 ) $ 1,275 $ (71 ) $ 471 $ (8 ) $ 1,305 $ (46 ) U.S. States and political subdivisions 420 (8 ) 181 (11 ) 242 (2 ) 183 (5 ) Foreign government 56 (1 ) 25 (1 ) 80 (1 ) 4 — Agency mortgage-backed residential 8,834 (215 ) 5,331 (282 ) 4,066 (19 ) 5,671 (137 ) Mortgage-backed residential 1,642 (35 ) 688 (58 ) 857 (2 ) 773 (32 ) Mortgage-backed commercial 91 (2 ) 18 (1 ) 76 (1 ) 21 — Asset-backed 479 (3 ) 71 (1 ) 220 (1 ) 91 — Corporate debt 885 (26 ) 254 (17 ) 529 (4 ) 194 (7 ) Total temporarily impaired available-for-sale securities $ 12,892 $ (309 ) $ 7,843 $ (442 ) $ 6,541 $ (38 ) $ 8,242 $ (227 ) Held-to-maturity securities Agency mortgage-backed residential $ 1,152 $ (33 ) $ 668 $ (50 ) $ 773 $ (5 ) $ 687 $ (32 ) Asset-backed retained certificates 24 — — — 35 — — — Total held-to-maturity debt securities $ 1,176 $ (33 ) $ 668 $ (50 ) $ 808 $ (5 ) $ 687 $ (32 )

Finance Receivables and Loans,

Finance Receivables and Loans, Net	6 Months Ended
	Jun. 30, 2018
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) June 30, 2018 December 31, 2017 Consumer automotive (a) $ 70,473 $ 68,071 Consumer mortgage Mortgage Finance (b) 13,328 11,657 Mortgage — Legacy (c) 1,803 2,093 Total consumer mortgage 15,131 13,750 Total consumer 85,604 81,821 Commercial Commercial and industrial Automotive 31,501 33,025 Other 4,027 3,887 Commercial real estate 4,412 4,160 Total commercial 39,940 41,072 Total finance receivables and loans (d) $ 125,544 $ 122,893 (a) Certain finance receivables and loans are included in fair value hedging relationships. Refer to Note 18 for additional information. (b) Includes loans originated as interest-only mortgage loans of $18 million and $20 million at June 30, 2018 , and December 31, 2017 , respectively, 36% of which are expected to start principal amortization in 2019 , and 48% in 2020 . The remainder of these loans have exited the interest-only period. (c) Includes loans originated as interest-only mortgage loans of $416 million and $496 million at June 30, 2018 , and December 31, 2017 , respectively, of which 99% have exited the interest-only period. (d) Totals include net unearned income, unamortized premiums and discounts, and deferred fees and costs of $612 million and $551 million at June 30, 2018 , and December 31, 2017 , respectively. The following tables present an analysis of the activity in the allowance for loan losses on finance receivables and loans. Three months ended June 30, 2018 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at April 1, 2018 $ 1,066 $ 74 $ 138 $ 1,278 Charge-offs (a) (296 ) (8 ) (2 ) (306 ) Recoveries 114 6 6 126 Net charge-offs (182 ) (2 ) 4 (180 ) Provision for loan losses 168 (4 ) (6 ) 158 Other 1 (2 ) 2 1 Allowance at June 30, 2018 $ 1,053 $ 66 $ 138 $ 1,257 (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 2017 Annual Report on Form 10-K for more information regarding our charge-off policies. Three months ended June 30, 2017 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at April 1, 2017 $ 941 $ 86 $ 128 $ 1,155 Charge-offs (a) (290 ) (6 ) — (296 ) Recoveries 91 6 — 97 Net charge-offs (199 ) — — (199 ) Provision for loan losses 260 (3 ) 12 269 Allowance at June 30, 2017 $ 1,002 $ 83 $ 140 $ 1,225 (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 2017 Annual Report on Form 10-K for more information regarding our charge-off policies. Six months ended June 30, 2018 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at January 1, 2018 $ 1,066 $ 79 $ 131 $ 1,276 Charge-offs (a) (661 ) (20 ) (2 ) (683 ) Recoveries 226 12 6 244 Net charge-offs (435 ) (8 ) 4 (439 ) Provision for loan losses 421 (3 ) 1 419 Other 1 (2 ) 2 1 Allowance at June 30, 2018 $ 1,053 $ 66 $ 138 $ 1,257 Allowance for loan losses at June 30, 2018 Individually evaluated for impairment $ 42 $ 24 $ 27 $ 93 Collectively evaluated for impairment 1,011 42 111 1,164 Finance receivables and loans at gross carrying value Ending balance $ 70,473 $ 15,131 $ 39,940 $ 125,544 Individually evaluated for impairment 480 228 198 906 Collectively evaluated for impairment 69,993 14,903 39,742 124,638 (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 2017 Annual Report on Form 10-K for more information regarding our charge-off policies. Six months ended June 30, 2017 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at January 1, 2017 $ 932 $ 91 $ 121 $ 1,144 Charge-offs (a) (631 ) (15 ) — (646 ) Recoveries 181 13 — 194 Net charge-offs (450 ) (2 ) — (452 ) Provision for loan losses 527 (6 ) 19 540 Other (b) (7 ) — — (7 ) Allowance at June 30, 2017 $ 1,002 $ 83 $ 140 $ 1,225 Allowance for loan losses at June 30, 2017 Individually evaluated for impairment $ 34 $ 31 $ 32 $ 97 Collectively evaluated for impairment 968 52 108 1,128 Finance receivables and loans at gross carrying value Ending balance $ 66,774 $ 11,294 $ 42,460 $ 120,528 Individually evaluated for impairment 380 242 151 773 Collectively evaluated for impairment 66,394 11,052 42,309 119,755 (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 2017 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 based on net carrying value. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Consumer automotive $ — $ 85 $ — $ 1,298 Consumer mortgage 4 3 5 6 Total sales and transfers $ 4 $ 88 $ 5 $ 1,304 The following table presents information about significant purchases of finance receivables and loans based on unpaid principal balance at the time of purchase. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Consumer automotive $ 233 $ 611 $ 401 $ 679 Consumer mortgage 852 809 2,147 1,136 Total purchases of finance receivables and loans $ 1,085 $ 1,420 $ 2,548 $ 1,815 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 June 30, 2018 Consumer automotive $ 1,706 $ 387 $ 248 $ 2,341 $ 68,132 $ 70,473 Consumer mortgage Mortgage Finance 50 4 11 65 13,263 13,328 Mortgage — Legacy 38 14 54 106 1,697 1,803 Total consumer mortgage 88 18 65 171 14,960 15,131 Total consumer 1,794 405 313 2,512 83,092 85,604 Commercial Commercial and industrial Automotive — — 21 21 31,480 31,501 Other 4 — — 4 4,023 4,027 Commercial real estate — — — — 4,412 4,412 Total commercial 4 — 21 25 39,915 39,940 Total consumer and commercial $ 1,798 $ 405 $ 334 $ 2,537 $ 123,007 $ 125,544 December 31, 2017 Consumer automotive $ 1,994 $ 478 $ 268 $ 2,740 $ 65,331 $ 68,071 Consumer mortgage Mortgage Finance 60 11 18 89 11,568 11,657 Mortgage — Legacy 43 25 62 130 1,963 2,093 Total consumer mortgage 103 36 80 219 13,531 13,750 Total consumer 2,097 514 348 2,959 78,862 81,821 Commercial Commercial and industrial Automotive 5 — 3 8 33,017 33,025 Other — — — — 3,887 3,887 Commercial real estate — — — — 4,160 4,160 Total commercial 5 — 3 8 41,064 41,072 Total consumer and commercial $ 2,102 $ 514 $ 351 $ 2,967 $ 119,926 $ 122,893 The following table presents the gross carrying value of our finance receivables and loans on nonaccrual status. ($ in millions) June 30, 2018 December 31, 2017 Consumer automotive $ 602 $ 603 Consumer mortgage Mortgage Finance 18 25 Mortgage — Legacy 87 92 Total consumer mortgage 105 117 Total consumer 707 720 Commercial Commercial and industrial Automotive 88 27 Other 104 44 Commercial real estate 6 1 Total commercial 198 72 Total consumer and commercial finance receivables and loans $ 905 $ 792 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 2017 Annual Report on Form 10-K for additional information. June 30, 2018 December 31, 2017 ($ in millions) Performing Nonperforming Total Performing Nonperforming Total Consumer automotive $ 69,871 $ 602 $ 70,473 $ 67,468 $ 603 $ 68,071 Consumer mortgage Mortgage Finance 13,310 18 13,328 11,632 25 11,657 Mortgage — Legacy 1,716 87 1,803 2,001 92 2,093 Total consumer mortgage 15,026 105 15,131 13,633 117 13,750 Total consumer $ 84,897 $ 707 $ 85,604 $ 81,101 $ 720 $ 81,821 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. June 30, 2018 December 31, 2017 ($ in millions) Pass Criticized (a) Total Pass Criticized (a) Total Commercial and industrial Automotive $ 28,890 $ 2,611 $ 31,501 $ 30,982 $ 2,043 $ 33,025 Other 3,260 767 4,027 2,986 901 3,887 Commercial real estate 4,193 219 4,412 4,023 137 4,160 Total commercial $ 36,343 $ 3,597 $ 39,940 $ 37,991 $ 3,081 $ 41,072 (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 2017 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 June 30, 2018 Consumer automotive $ 491 $ 480 $ 117 $ 363 $ 42 Consumer mortgage Mortgage Finance 10 10 4 6 — Mortgage — Legacy 223 218 63 155 24 Total consumer mortgage 233 228 67 161 24 Total consumer 724 708 184 524 66 Commercial Commercial and industrial Automotive 88 88 16 72 12 Other 116 104 40 64 15 Commercial real estate 6 6 4 2 — Total commercial 210 198 60 138 27 Total consumer and commercial finance receivables and loans $ 934 $ 906 $ 244 $ 662 $ 93 December 31, 2017 Consumer automotive $ 438 $ 430 $ 91 $ 339 $ 36 Consumer mortgage Mortgage Finance 8 8 4 4 — Mortgage — Legacy 228 223 58 165 27 Total consumer mortgage 236 231 62 169 27 Total consumer 674 661 153 508 63 Commercial Commercial and industrial Automotive 27 27 9 18 3 Other 54 44 10 34 11 Commercial real estate 1 1 — 1 — Total commercial 82 72 19 53 14 Total consumer and commercial finance receivables and loans $ 756 $ 733 $ 172 $ 561 $ 77 (a) Adjusted for charge-offs. The following tables present average balance and interest income for our impaired finance receivables and loans. 2018 2017 Three months ended June 30, ($ in millions) Average balance Interest income Average balance Interest income Consumer automotive $ 472 $ 7 $ 391 $ 5 Consumer mortgage Mortgage Finance 9 — 8 — Mortgage — Legacy 219 3 238 3 Total consumer mortgage 228 3 246 3 Total consumer 700 10 637 8 Commercial Commercial and industrial Automotive 78 1 54 1 Other 82 — 73 8 Commercial real estate 5 — 6 — Total commercial 165 1 133 9 Total consumer and commercial finance receivables and loans $ 865 $ 11 $ 770 $ 17 2018 2017 Six months ended June 30, ($ in millions) Average balance Interest income Average balance Interest income Consumer automotive $ 462 $ 14 $ 381 $ 10 Consumer mortgage Mortgage Finance 9 — 8 — Mortgage — Legacy 220 5 239 5 Total consumer mortgage 229 5 247 5 Total consumer 691 19 628 15 Commercial Commercial and industrial Automotive 61 2 47 1 Other 66 — 77 8 Commercial real estate 4 — 6 — Total commercial 131 2 130 9 Total consumer and commercial finance receivables and loans $ 822 $ 21 $ 758 $ 24 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 $791 million and $712 million at June 30, 2018 , and December 31, 2017 , respectively. Total commitments to lend additional funds to borrowers whose terms had been modified in a TDR were $7 million and $6 million at June 30, 2018 , and December 31, 2017 , respectively. Refer to Note 1 to the Consolidated Financial Statements in our 2017 Annual Report on Form 10-K for additional information. The following tables present information related to finance receivables and loans recorded at gross carrying value modified in connection with a TDR during the period. 2018 2017 Three months ended June 30, ($ 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 5,898 $ 107 $ 93 5,762 $ 103 $ 88 Consumer mortgage Mortgage Finance 7 2 2 — — — Mortgage — Legacy 27 6 7 19 3 2 Total consumer mortgage 34 8 9 19 3 2 Total consumer 5,932 115 102 5,781 106 90 Commercial Commercial and industrial Automotive 3 4 4 — — — Other 2 55 51 1 21 21 Total commercial 5 59 55 1 21 21 Total consumer and commercial finance receivables and loans 5,937 $ 174 $ 157 5,782 $ 127 $ 111 2018 2017 Six months ended June 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 12,940 $ 235 $ 203 12,209 $ 218 $ 187 Consumer mortgage Mortgage Finance 8 3 3 1 — — Mortgage — Legacy 89 16 16 72 15 14 Total consumer mortgage 97 19 19 73 15 14 Total consumer 13,037 254 222 12,282 233 201 Commercial Commercial and industrial Automotive 3 4 4 — — — Other 2 55 51 2 44 44 Total commercial 5 59 55 2 44 44 Total consumer and commercial finance receivables and loans 13,042 $ 313 $ 277 12,284 $ 277 $ 245 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 2017 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. 2018 2017 Three months ended June 30, ($ in millions) Number of loans Gross carrying value Charge-off amount Number of loans Gross carrying value Charge-off amount Consumer automotive 2,425 $ 29 $ 17 2,143 $ 25 $ 17 Consumer mortgage Mortgage Finance — — — — — — Mortgage — Legacy 1 — — — — — Total consumer finance receivables and loans 2,426 $ 29 $ 17 2,143 $ 25 $ 17 2018 2017 Six months ended June 30, ($ in millions) Number of loans Gross carrying value Charge-off amount Number of loans Gross carrying value Charge-off amount Consumer automotive 4,751 $ 57 $ 35 4,132 $ 49 $ 33 Consumer mortgage Mortgage Finance — — — 1 1 — Mortgage — Legacy 1 — — — — — Total consumer finance receivables and loans 4,752 $ 57 $ 35 4,133 $ 50 $ 33

Investment in Operating Leases,

Investment in Operating Leases, Net	6 Months Ended
	Jun. 30, 2018
Leases, Operating [Abstract]
Lessor, Operating Leases [Text Block]	Investment in Operating Leases, Net Investments in operating leases were as follows. ($ in millions) June 30, 2018 December 31, 2017 Vehicles $ 10,260 $ 10,556 Accumulated depreciation (1,621 ) (1,815 ) Investment in operating leases, net $ 8,639 $ 8,741 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 June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Depreciation expense on operating lease assets (excluding remarketing gains) $ 281 $ 353 $ 572 $ 739 Remarketing gains (16 ) (32 ) (34 ) (29 ) Net depreciation expense on operating lease assets $ 265 $ 321 $ 538 $ 710

Securitizations and Variable In

Securitizations and Variable Interest Entities	6 Months Ended
	Jun. 30, 2018
Securitizations And Variable Interest Entities [Abstract]
Variable Interest Entity Disclosure [Text Block]	Securitizations and Variable Interest Entities We securitize, transfer, and service consumer and commercial automotive loans, and operating leases. We often securitize these loans and notes secured by operating leases (collectively referred to as financial assets) through the use of 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 which may, or may not, be included on our Condensed Consolidated Balance Sheet . The transaction-specific SPEs involved in our securitization 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. The nature, purpose, and activities of nonconsolidated securitization entities are similar to those of our consolidated securitization entities with the primary difference being the nature and extent of our continuing involvement. Additionally, to qualify for off-balance sheet treatment, transfers of financial assets must meet appropriate sale accounting conditions. For nonconsolidated securitization entities, the transferred financial assets are removed from our balance sheet provided the conditions for sale accounting are met. The financial assets obtained from the securitization are primarily reported as cash, or retained interests (if applicable). Liabilities incurred as part of these securitization transactions, such as representation and warranty provisions, are recorded at fair value at the time of sale and are reported as accrued expenses and other liabilities on our Consolidated Balance Sheet. Upon the sale of the loans, we recognize a gain or loss on sale for the difference between the assets recognized, the assets derecognized, and the liabilities recognized as part of the transaction. We had no pretax gain on sales of financial assets into nonconsolidated VIEs for both the three months and six months ended June 30, 2018 , and the three months ended June 30, 2017. We had a pretax gain of $2 million for the six months ended June 30, 2017. We provide long-term guarantee contracts to investors in certain nonconsolidated affordable housing entities and have extended a line of credit to provide liquidity. Since we do not have control over the entities or the power to make decisions, we do not consolidate the entities and our involvement is limited to the guarantee and the line of credit. We have involvement with various other nonconsolidated equity investments, including affordable housing entities and venture capital funds and loan funds. We do not consolidate these entities and our involvement is limited to our outstanding investment, additional capital committed to these funds plus any previously recognized low income housing tax credits that are subject to recapture. Refer to Note 11 to the Consolidated Financial Statements in our 2017 Annual Report on Form 10-K for further description of our securitization activities and our involvement with VIEs. The following table presents our involvement in consolidated and nonconsolidated VIEs in which we hold variable interests. For additional detail related to the assets and liabilities of consolidated variable interest entities refer to the Condensed Consolidated Balance Sheet. ($ 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 June 30, 2018 On-balance sheet variable interest entities Consumer automotive $ 18,806 (b) $ 8,787 (c) Commercial automotive 9,945 3,595 Off-balance sheet variable interest entities Consumer automotive 28 (d) — $ 1,388 $ 1,416 (e) Commercial other 739 (f) 344 (g) — 968 (h) Total $ 29,518 $ 12,726 $ 1,388 $ 2,384 December 31, 2017 On-balance sheet variable interest entities Consumer automotive $ 17,597 (b) $ 7,677 (c) Commercial automotive 12,550 2,558 Off-balance sheet variable interest entities Consumer automotive 37 (d) — $ 1,964 $ 2,001 (e) Commercial other 592 (f) 248 (g) — 790 (h) Total $ 30,776 $ 10,483 $ 1,964 $ 2,791 (a) Asset values represent the current unpaid principal balance of outstanding consumer finance receivables and loans within the VIEs. (b) Includes $8.5 billion of assets that were not encumbered by VIE beneficial interests held by third parties at both June 30, 2018 , and December 31, 2017 . Ally or consolidated affiliates hold the interests in these assets. (c) Includes $25 million and $29 million of liabilities that were not obligations to third-party beneficial interest holders at June 30, 2018 , and December 31, 2017 , respectively. (d) Represents retained notes and certificated residual interests, of which $27 million and $36 million were classified as held-to-maturity securities at June 30, 2018 , and December 31, 2017 , respectively, and $1 million was classified as other assets at both June 30, 2018 , and December 31, 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. (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 consumer automotive assets (e.g., servicing) that were outstanding during the six months ended June 30, 2018 , and 2017. Additionally, this table contains information regarding cash flows received from and paid to nonconsolidated securitization entities that existed during each period. Six months ended June 30, ($ in millions) Consumer automotive Consumer mortgage 2018 Cash disbursements for repurchases during the period $ (2 ) $ — Servicing fees 10 — Cash flows received on retained interests in securitization entities 9 — Representation and warranty recoveries — 2 2017 Cash proceeds from transfers completed during the period $ 1,187 $ — Cash disbursements for repurchases during the period (a) (491 ) — Servicing fees 18 — Cash flows received on retained interests in securitization entities 10 — Other cash flows 4 — (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 present quantitative information about delinquencies and net credit losses for off-balance sheet securitizations and whole-loan sales where we have continuing involvement. Total amount Amount 60 days or more past due ($ in millions) June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 Off-balance sheet securitization entities Consumer automotive $ 1,388 $ 1,964 $ 12 $ 16 Total off-balance sheet securitization entities 1,388 1,964 12 16 Whole-loan sales (a) 964 1,399 3 4 Total $ 2,352 $ 3,363 $ 15 $ 20 (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 June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Off-balance sheet securitization entities Consumer automotive $ 2 $ 3 $ 5 $ 6 Total off-balance sheet securitization entities 2 3 5 6 Whole-loan sales (a) — 1 1 2 Total $ 2 $ 4 $ 6 $ 8 (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	6 Months Ended
	Jun. 30, 2018
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 $8 million and $16 million during the three months and six months ended June 30, 2018 , respectively, compared to $14 million and $30 million during the three months and six months ended June 30, 2017 . Automotive Finance Serviced Assets The current unpaid principal balance and any related unamortized deferred fees and costs of total serviced automotive finance loans and net investment in operating leases outstanding were as follows. ($ in millions) June 30, 2018 December 31, 2017 On-balance sheet automotive finance loans and leases Consumer automotive $ 69,701 $ 67,631 Commercial automotive 35,645 37,058 Operating leases 8,613 8,682 Other 111 121 Off-balance sheet automotive finance loans Securitizations 1,392 1,977 Whole-loan sales 969 1,409 Total serviced automotive finance loans and leases $ 116,431 $ 116,878

Other Assets

Other Assets	6 Months Ended
	Jun. 30, 2018
Other Assets [Abstract]
Other Assets Disclosure [Text Block]	Other Assets The components of other assets were as follows. ($ in millions) June 30, 2018 December 31, 2017 Property and equipment at cost $ 1,161 $ 1,064 Accumulated depreciation (648 ) (608 ) Net property and equipment 513 456 Nonmarketable equity investments (a) 1,276 1,233 Restricted cash collections for securitization trusts (b) 796 812 Accrued interest and rent receivables 548 550 Net deferred tax assets 455 461 Other accounts receivable 289 116 Goodwill (c) 240 240 Restricted cash and cash equivalents (d) 116 94 Cash reserve deposits held for securitization trusts (e) 103 111 Fair value of derivative contracts in receivable position (f) 63 39 Cash collateral placed with counterparties 35 29 Other assets 1,580 1,522 Total other assets $ 6,014 $ 5,663 (a) Includes investments in FHLB stock of $790 million and $745 million at June 30, 2018 , and December 31, 2017, respectively; FRB stock of $447 million and $445 million at June 30, 2018 , and December 31, 2017, respectively; and equity securities without a readily determinable fair value of $39 million at June 30, 2018 , measured at cost with adjustments for impairment and observable changes in price. During the three months and six months ended June 30, 2018 , we recorded $1 million in impairment related to equity securities without a readily determinable fair value. (b) Represents cash collections from customer payments on securitized receivables. These funds are distributed to investors as payments on the related secured debt. (c) Includes goodwill of $27 million within our Insurance operations at both June 30, 2018 , and December 31, 2017 ; $193 million within Corporate and Other at both June 30, 2018 , and December 31, 2017 ; and $20 million within Automotive Finance operations at both June 30, 2018 , and December 31, 2017 . No changes to the carrying amount of goodwill were recorded during the six months ended June 30, 2018 . (d) Primarily represents a number of arrangements with third parties where certain restrictions are placed on balances we hold due to collateral agreements associated with operational processes with a third-party bank, or letter of credit arrangements and corresponding collateral requirements. (e) Represents credit enhancement in the form of cash reserves for various securitization transactions. (f) For additional information on derivative instruments and hedging activities, refer to Note 18 .

Deposit Liabilities

Deposit Liabilities	6 Months Ended
	Jun. 30, 2018
Deposits [Abstract]
Deposit Liabilities Disclosures [Text Block]	Deposit Liabilities Deposit liabilities consisted of the following. ($ in millions) June 30, 2018 December 31, 2017 Noninterest-bearing deposits $ 153 $ 108 Interest-bearing deposits Savings and money market checking accounts 50,958 49,267 Certificates of deposit 47,617 43,869 Dealer deposits 6 12 Total deposit liabilities $ 98,734 $ 93,256 At June 30, 2018 , and December 31, 2017 , certificates of deposit included $19.9 billion and $18.9 billion , respectively, of those in denominations of $100 thousand or more. At both June 30, 2018 , and December 31, 2017 , certificates of deposit included $5.3 billion of those in denominations in excess of $250 thousand federal insurance limits.

Debt

Debt	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	Debt Short-term Borrowings The following table presents the composition of our short-term borrowings portfolio. June 30, 2018 December 31, 2017 ($ in millions) Unsecured Secured (a) Total Unsecured Secured (a) Total Demand notes $ 2,666 $ — $ 2,666 $ 3,171 $ — $ 3,171 Federal Home Loan Bank — 3,475 3,475 — 7,350 7,350 Financial instruments sold under agreements to repurchase — 967 967 — 892 892 Total short-term borrowings $ 2,666 $ 4,442 $ 7,108 $ 3,171 $ 8,242 $ 11,413 (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 June 30, 2018 , the financial instruments sold under agreements to repurchase consisted of $276 million of U.S. Treasury and $691 million of agency mortgage-backed residential debt securities set to mature as follows: $530 million within 30 days, and $437 million within 61 to 90 days. Refer to Note 6 and Note 21 for further details. 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. In some instances, we may place or receive cash collateral with counterparties under collateral arrangements associated with our repurchase agreements. At June 30, 2018 , we placed cash collateral totaling $4 million and received cash collateral totaling $1 million and noncash collateral totaling $1 million . At December 31, 2017 , we placed cash collateral totaling $10 million and received cash collateral totaling $1 million . Long-term Debt The following table presents the composition of our long-term debt portfolio. June 30, 2018 December 31, 2017 ($ in millions) Unsecured Secured Total Unsecured Secured Total Long-term debt Due within one year $ 2,740 $ 8,016 $ 10,756 $ 3,482 $ 7,499 $ 10,981 Due after one year (a) 11,139 25,334 36,473 11,909 21,128 33,037 Fair value adjustment (b) 168 (69 ) 99 240 (32 ) 208 Total long-term debt (c) $ 14,047 $ 33,281 $ 47,328 $ 15,631 $ 28,595 $ 44,226 (a) Includes $2.6 billion of trust preferred securities at both June 30, 2018 , and December 31, 2017. (b) Represents the basis adjustment associated with the application of hedge accounting on certain of our long-term debt positions. Refer to Note 18 for additional information. (c) Includes advances from the FHLB of Pittsburgh of $14.7 billion and $10.3 billion at June 30, 2018 , and December 31, 2017, respectively. The following table presents the scheduled remaining maturity of long-term debt at June 30, 2018 , assuming no early redemptions will occur. The actual payment of secured debt may vary based on the payment activity of the related pledged assets. ($ in millions) 2018 2019 2020 2021 2022 2023 and thereafter Fair value adjustment Total Unsecured Long-term debt $ 1,991 $ 1,681 $ 2,251 $ 663 $ 1,066 $ 7,414 $ 168 $ 15,234 Original issue discount (52 ) (38 ) (39 ) (43 ) (47 ) (968 ) — (1,187 ) Total unsecured 1,939 1,643 2,212 620 1,019 6,446 168 14,047 Secured Long-term debt 3,356 7,995 7,430 8,484 4,562 1,523 (69 ) 33,281 Total long-term debt $ 5,295 $ 9,638 $ 9,642 $ 9,104 $ 5,581 $ 7,969 $ 99 $ 47,328 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. June 30, 2018 December 31, 2017 ($ in millions) Total (a) Ally Bank Total (a) Ally Bank Investment securities (b) $ 7,902 $ 6,995 $ 8,371 $ 7,443 Mortgage assets held-for-investment and lending receivables 14,943 14,943 13,579 13,579 Consumer automotive finance receivables 18,965 9,621 19,787 6,200 Commercial automotive finance receivables 14,252 14,211 16,567 16,472 Operating leases 267 — 457 — Total assets restricted as collateral (c) (d) $ 56,329 $ 45,770 $ 58,761 $ 43,694 Secured debt $ 37,723 (e) $ 27,990 $ 36,837 (e) $ 23,278 (a) Ally Bank is a component of the total column. (b) A portion of the restricted investment securities at June 30, 2018 , and December 31, 2017 , 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 $26.3 billion and $25.2 billion at June 30, 2018 , and December 31, 2017 , 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 $2.4 billion and $2.3 billion at June 30, 2018 , and December 31, 2017 , respectively. These assets were composed of consumer automotive finance receivables and loans. 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 11 for additional information. (e) Includes $4.4 billion and $8.2 billion of short-term borrowings at June 30, 2018 , and December 31, 2017 , respectively. Trust Preferred Securities At June 30, 2018 , 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 are payable at an annual rate equal to three-month London interbank offer rate plus 5.785% payable quarterly in arrears. 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 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 June 30, 2018 , Ally Bank had exclusive access to $2.5 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 June 30, 2018 , all of our $9.2 billion of committed capacity was revolving. Our revolving facilities generally have an original tenor ranging from 364 days to two years. As of June 30, 2018 , we had $7.6 billion of committed funding capacity from revolving facilities with a remaining tenor greater than 364 days. Committed Funding Facilities Outstanding Unused capacity (a) Total capacity ($ in millions) June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 Bank funding Secured $ 2,500 $ 1,785 $ — $ 890 $ 2,500 $ 2,675 Parent funding Secured 3,855 6,330 2,870 2,920 6,725 9,250 Total committed facilities $ 6,355 $ 8,115 $ 2,870 $ 3,810 $ 9,225 $ 11,925 (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.

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	6 Months Ended
	Jun. 30, 2018
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) June 30, 2018 December 31, 2017 Accounts payable $ 369 $ 746 Employee compensation and benefits 188 248 Reserves for insurance losses and loss adjustment expenses 149 140 Fair value of derivative contracts in payable position (a) 65 41 Cash collateral received from counterparties 39 17 Deferred revenue 28 32 Other liabilities 673 556 Total accrued expenses and other liabilities $ 1,511 $ 1,780 (a) For additional information on derivative instruments and hedging activities, refer to Note 18 .

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	6 Months Ended
	Jun. 30, 2018
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive Loss The following table presents changes, net of tax, in each component of accumulated other comprehensive loss. ($ 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 Balance at December 31, 2016 $ (273 ) $ 14 $ 8 $ (90 ) $ (341 ) 2017 net change 96 — 1 (1 ) 96 Balance at June 30, 2017 $ (177 ) $ 14 $ 9 $ (91 ) $ (245 ) Balance at December 31, 2017, before cumulative effect of adjustments $ (173 ) $ 16 $ 11 $ (89 ) $ (235 ) Cumulative effect of changes in accounting principles, net of tax (c) Adoption of Accounting Standards Update 2016-01 27 — — — 27 Adoption of Accounting Standards Update 2018-02 (40 ) 4 — (6 ) (42 ) Balance at January 1, 2018, after cumulative effect of adjustments (186 ) 20 11 (95 ) (250 ) 2018 net change (412 ) (1 ) 17 (2 ) (398 ) Balance at June 30, 2018 $ (598 ) $ 19 $ 28 $ (97 ) $ (648 ) (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 18 . (c) Refer to the section titled Recently Adopted Accounting Standards in Note 1 for additional information. The following tables present the before- and after-tax changes in each component of accumulated other comprehensive (loss) income. Three months ended June 30, 2018 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized losses arising during the period $ (95 ) $ 22 $ (73 ) Less: Net realized gains reclassified to income from continuing operations 1 (a) — (b) 1 Net change (96 ) 22 (74 ) Translation adjustments Net unrealized losses arising during the period (3 ) 1 (2 ) Net investment hedges (c) Net unrealized gains arising during the period 3 (1 ) 2 Cash flow hedges (c) Net unrealized gains arising during the period 5 (2 ) 3 Defined benefit pension plans Net unrealized gains arising during the period 1 — 1 Other comprehensive loss $ (90 ) $ 20 $ (70 ) (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 18 . Three months ended June 30, 2017 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 132 $ (37 ) $ 95 Less: Net realized gains reclassified to income from continuing operations 23 (a) (3 ) (b) 20 Net change 109 (34 ) 75 Translation adjustments Net unrealized gains arising during the period 4 (1 ) 3 Net investment hedges (c) Net unrealized losses arising during the period (4 ) 1 (3 ) Cash flow hedges (c) Net unrealized gains arising during the period 1 — 1 Other comprehensive income $ 110 $ (34 ) $ 76 (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 18 . Six months ended June 30, 2018 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized losses arising during the period $ (531 ) $ 125 $ (406 ) Less: Net realized gains reclassified to income from continuing operations 7 (a) (1 ) (b) 6 Net change (538 ) 126 (412 ) Translation adjustments Net unrealized losses arising during the period (8 ) 2 (6 ) Net investment hedges (c) Net unrealized gains arising during the period 7 (2 ) 5 Cash flow hedges (c) Net unrealized gains arising during the period 23 (6 ) 17 Defined benefit pension plans Net unrealized losses arising during the period (2 ) — (2 ) Other comprehensive loss $ (518 ) $ 120 $ (398 ) (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 18 . Six months ended June 30, 2017 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 183 $ (42 ) $ 141 Less: Net realized gains reclassified to income from continuing operations 50 (a) (5 ) (b) 45 Net change 133 (37 ) 96 Translation adjustments Net unrealized gains arising during the period 6 (2 ) 4 Net investment hedges (c) Net unrealized losses arising during the period (6 ) 2 (4 ) Cash flow hedges (c) Net unrealized gains arising during the period 1 — 1 Defined benefit pension plans Net unrealized losses arising during the period (1 ) — (1 ) Other comprehensive income $ 133 $ (37 ) $ 96 (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 18 .

Earnings per Common Share

Earnings per Common Share	6 Months Ended
	Jun. 30, 2018
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 June 30, Six months ended June 30, ($ in millions, except per share data; shares in thousands) (a) 2018 2017 2018 2017 Net income from continuing operations attributable to common stockholders $ 348 $ 254 $ 600 $ 467 Income (loss) from discontinued operations, net of tax 1 (2 ) (1 ) (1 ) Net income attributable to common stockholders $ 349 $ 252 $ 599 $ 466 Basic weighted-average common shares outstanding (b) 430,628 457,891 433,405 461,904 Diluted weighted-average common shares outstanding (b) 432,554 458,819 435,727 462,802 Basic earnings per common share Net income from continuing operations $ 0.81 $ 0.55 $ 1.38 $ 1.01 Loss from discontinued operations, net of tax — (0.01 ) — — Net income $ 0.81 $ 0.55 $ 1.38 $ 1.01 Diluted earnings per common share Net income from continuing operations $ 0.80 $ 0.55 $ 1.38 $ 1.01 Loss from discontinued operations, net of tax — (0.01 ) — — Net income $ 0.81 $ 0.55 $ 1.37 $ 1.01 (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 six months ended June 30, 2018 , and 2017 .

Regulatory Capital and Other Re

Regulatory Capital and Other Regulatory Matters	6 Months Ended
	Jun. 30, 2018
Regulatory Capital Requirements [Abstract]
Regulatory Capital Requirements under Banking Regulations [Text Block]	Regulatory Capital and Other Regulatory Matters The FRB and other U.S. banking agencies have adopted risk-based and leverage capital standards that establish minimum capital-to-asset ratios for BHCs, like Ally, and depository institutions, like Ally Bank. The risk-based capital ratios are based on a banking organization’s risk-weighted assets (RWAs), which are generally determined under the Basel III standardized approach applicable to Ally and Ally Bank by (1) assigning on-balance sheet exposures to broad risk weight categories according to the counterparty or, if relevant, the guarantor or collateral (with higher risk weights assigned to categories of exposures perceived as representing greater risk), and (2) multiplying off-balance sheet exposures by specified credit conversion factors to calculate credit equivalent amounts and assigning those credit equivalent amounts to the relevant risk weight categories. The leverage ratio, in contrast, is based on an institution’s average unweighted on-balance sheet exposures. Ally and 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. 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 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 an 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 and Ally Bank 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 risk-based capital ratios, Ally and Ally Bank are 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 would result in restrictions on the ability of Ally and Ally Bank to make capital distributions, including dividend payments and stock repurchases and redemptions, and to pay discretionary bonuses to executive officers. U.S. Basel III also subjects Ally and Ally Bank to a minimum Tier 1 leverage ratio of 4% . 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. For example, subject to certain exceptions (e.g., certain debt or equity issued to the U.S. government under the Emergency Economic Stabilization Act), trust preferred and other hybrid securities were excluded from 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 under U.S. Basel III 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 stock 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 RWAs by, among other things, modifying certain risk weights and the methods for calculating RWAs for certain types of assets and exposures. Ally and Ally Bank are subject to the U.S. Basel III standardized approach for counterparty credit risk, but not to the U.S. Basel III advanced approaches for credit risk or operational risk. Ally is also not subject to the U.S. market risk capital rule, which applies only to banking organizations with significant trading assets and liabilities. On May 24, 2018, the Economic Growth, Regulatory Relief, and Consumer Protection Act was enacted. This legislation includes targeted amendments to the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 and other financial services laws, including amendments that affect whether and, if so, how the FRB applies enhanced prudential standards to BHCs like us with total consolidated assets equal to or greater than $100 billion and less than $250 billion . While we currently anticipate that this legislation may result in regulatory and supervisory frameworks that are more tailored to our risk profile, such a result generally depends on future action by the U.S. banking agencies and, as a result, cannot be predicted with any certainty. On April 13, 2018, the FRB and other U.S. banking agencies proposed a revision to their regulatory capital rules to address the regulatory capital treatment related to ASU 2016-13, which Ally plans to adopt effective January 1, 2020, as further described in Note 1 . We expect the implementation of ASU 2016-13 will significantly increase our allowance for credit losses upon adoption. If finalized, the proposed changes to the regulatory capital rules would allow Ally to phase in the impact to our regulatory capital as a result of the increase to our allowance for credit losses on a straight-line basis over a three-year period. In addition, the U.S. banking agencies are proposing to make amendments to the stress testing regulations that would exclude the impact of the adoption of ASU 2016-13 until the 2020 stress testing cycle. We continue to monitor and evaluate these regulatory developments. Until the U.S. banking agencies decide whether and, if so, how to amend their regulatory capital rules to account for ASU 2016-13, its ultimate impact on our regulatory capital and, therefore, our business, results of operations, and financial condition is unclear. On April 10, 2018, the FRB issued a proposal that would seek to more closely align forward-looking stress testing results with the FRB’s non-stress capital requirements for banking organizations with $50 billion or more in assets. The proposal would introduce a “stress capital buffer” based on firm-specific stress test performance, which would effectively replace the capital conservation buffer for determining non-stress capital requirements. The proposal would also incorporate several other changes to the CCAR process including eliminating the CCAR quantitative objection, narrowing the set of planned capital actions assumed to occur in the stress scenario and eliminating the thirty percent dividend payout ratio as a criterion for heightened scrutiny of a firm’s capital plan, among other proposed changes. If finalized, the rule would be effective on December 31, 2018, and a firm’s first stress buffer requirements would generally be effective on October 1, 2019. We are currently evaluating the effect this proposal will have on our capital planning and stress testing requirements. In December 2017, the Basel Committee approved revisions to the global Basel III capital framework (commonly known as Basel IV), many of which—if adopted in the United States—could heighten regulatory capital standards even more. At this time, it is not clear how all of these proposals and revisions will be harmonized and finalized in the United States. 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 $447 million of FRB stock at June 30, 2018 . In addition, in connection with the application for membership in the Federal Reserve System, Ally Bank made commitments to the FRB relating to capital, liquidity, and business plan requirements. These commitments were consistent with the prior requirements under the now-terminated Capital and Liquidity Maintenance Agreement with the Federal Deposit Insurance Corporation (FDIC), including the requirement to maintain capital at a level such that Ally Bank’s Tier 1 leverage ratio was at least 15% . On August 22, 2017, banking agencies lifted the capital, liquidity, and business plan commitments that Ally Bank had made in connection with its application for membership in the Federal Reserve System, including the commitment to maintain a Tier 1 leverage ratio of at least 15% . Compliance with capital requirements is a strategic priority for Ally. We expect to be in compliance with all applicable requirements within the established timeframes. The following table summarizes our capital ratios under the U.S. Basel III capital framework. June 30, 2018 December 31, 2017 Required minimum (a) Well-capitalized minimum ($ in millions) Amount Ratio Amount Ratio Capital ratios Common Equity Tier 1 (to risk-weighted assets) Ally Financial Inc. $ 13,265 9.37 % $ 13,237 9.53 % 4.50 % (b) Ally Bank 16,591 13.65 17,059 15.04 4.50 6.50 % Tier 1 (to risk-weighted assets) Ally Financial Inc. $ 15,698 11.09 % $ 15,628 11.25 % 6.00 % 6.00 % Ally Bank 16,591 13.65 17,059 15.04 6.00 8.00 Total (to risk-weighted assets) Ally Financial Inc. $ 17,926 12.66 % $ 17,974 12.94 % 8.00 % 10.00 % Ally Bank 17,557 14.45 17,886 15.77 8.00 10.00 Tier 1 leverage (to adjusted quarterly average assets) (c) Ally Financial Inc. $ 15,698 9.21 % $ 15,628 9.53 % 4.00 % (b) Ally Bank 16,591 11.50 17,059 12.87 4.00 5.00 % (a) In addition to the minimum risk-based capital requirements for common equity Tier 1 capital, Tier 1 capital, and total capital ratios, Ally and Ally Bank were required to maintain a minimum capital conservation buffer of 1.875% and 1.25% at June 30, 2018, and December 31, 2017, respectively, which ultimately increases to 2.5% on January 1, 2019. (b) Currently, there is no ratio component for determining whether a BHC is “well-capitalized.” (c) Federal regulatory reporting guidelines require the calculation of adjusted quarterly average assets using a daily average methodology. At June 30, 2018 , Ally and Ally Bank were “well-capitalized” and met all applicable capital requirements to which each was subject. Capital Planning and Stress Tests 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 a proposed capital plan to the FRB. Ally’s proposed capital plan must include an assessment of our expected uses and sources of capital and a description of all planned capital actions over a nine-quarter planning horizon, including any issuance of a debt or equity capital instrument, any dividend or other capital distribution, and any similar action that the FRB determines could have an impact on Ally’s capital. The proposed capital plan must also include a discussion of how Ally, under expected and stressful conditions, will maintain capital commensurate with its risks and above the minimum regulatory capital ratios, and serve as a source of strength to Ally Bank. The FRB will either object to Ally’s proposed capital plan, in whole or in part, or provide a notice of non-objection to Ally’s proposed capital plan, and must do so before Ally may take any capital action. In addition, even if the FRB does not object to our capital plan, Ally may be precluded from or limited in paying dividends or other capital distributions without the FRB’s approval under certain circumstances—for example, when we would not meet minimum regulatory capital ratios and capital buffers after giving effect to the distributions. As part of the 2017 Comprehensive Capital Analysis and Review (CCAR) process, 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 increases in the quarterly cash dividend on common stock and in our share repurchase program. The following table presents information related to our common stock for each quarter since the commencement of our common stock repurchase programs and initiation of a quarterly cash dividend on common stock. Common stock repurchased during period (a) Number of common shares outstanding Cash dividends declared per common share (b) ($ in millions, except per share data; shares in thousands) Approximate dollar value Number of shares Beginning of period End of period 2016 Third quarter $ 159 8,298 483,753 475,470 $ 0.08 Fourth quarter 167 8,745 475,470 467,000 0.08 2017 First quarter $ 169 8,097 467,000 462,193 $ 0.08 Second quarter 204 10,485 462,193 452,292 0.08 Third quarter 190 8,507 452,292 443,796 0.12 Fourth quarter 190 7,033 443,796 437,054 0.12 2018 First quarter $ 185 6,473 437,054 432,691 $ 0.13 Second quarter 195 7,280 432,691 425,752 0.13 (a) Includes shares of common stock withheld to cover income taxes owed by participants in our share-based incentive plans. (b) On July 13, 2018 , the Ally Board of Directors (the Board) declared a quarterly cash dividend of $0.15 per share on all common stock, payable on August 15, 2018 . Refer to Note 25 for further information regarding this common stock dividend. Ally submitted its 2018 capital plan and stress test results to the FRB on April 5, 2018. On June 21, 2018, we publicly disclosed summary results of the stress test under the severely adverse scenario in accordance with applicable regulatory requirements. On June 28, 2018, we received from the FRB a non-objection to our capital plan, which includes increases in both our share repurchase program and our planned dividends. Consistent with the capital plan, the Board authorized a 32% increase in our share repurchase program, permitting us to repurchase up to $1.0 billion of our common stock from time to time from the third quarter of 2018 through the second quarter of 2019. Also consistent with the capital plan, on July 13, 2018 , the Board declared a quarterly cash dividend of $0.15 per share of our common stock, which is a $0.02 or 15% increase relative to the dividend declared in the prior quarter. Refer to Note 25 for further information on the most recent 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 Board, and other considerations including the degree of severity of stress scenarios assigned by the FRB as part of the CCAR process. In January 2017, the FRB amended the capital planning and stress testing rules, effective for the 2017 cycle and beyond. As a result of this amendment, the FRB may no longer object to the capital plan of a large and noncomplex BHC, like Ally, on the basis of qualitative deficiencies in its capital planning process. Instead, the qualitative assessment of Ally’s capital planning process is now conducted outside of CCAR through the supervisory review process. The amendment also decreased the de minimis threshold for the amount of capital that Ally could distribute to stockholders outside of an approved capital plan without seeking prior approval of the FRB, and modified Ally’s reporting requirements to reduce unnecessary burdens.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]	Derivative Instruments and Hedging Activities We enter into derivative instruments, such as interest rate, foreign-currency, and equity swaps, futures, forwards, and options in connection with our risk management activities. 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. Interest Rate Risk We monitor our mix of fixed- and variable-rate assets and liabilities and 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 these trades 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 securities within our available-for-sale portfolio, and pay-fixed swaps designated as fair value hedges of closed portfolios of fixed-rate held-for-investment retail automotive loan assets in which the hedged item is the last layer expected to be remaining at the end of the hedging relationship. 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 and deposit liabilities. We may also execute economic hedges, which consist of interest rate swaps, interest rate caps, forwards, futures, options, and swaptions to mitigate interest rate risk. 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 any foreign-denominated debt, centralized lending, 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 and receive 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 three months ended June 30, 2018 , or 2017 . We placed cash collateral totaling $31 million and noncash collateral totaling $151 million at June 30, 2018 , and $20 million and $97 million at December 31, 2017 , respectively, in accounts maintained by counterparties. This amount primarily relates to collateral posted to support our derivative positions. This amount also excludes cash and noncash collateral pledged under repurchase agreements. Refer to Note 13 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 $38 million and noncash collateral totaling $11 million at June 30, 2018 , and $17 million and $2 million at December 31, 2017 , respectively, in accounts maintained by counterparties. These amounts exclude cash and noncash collateral pledged under repurchase agreements. Refer to Note 13 for details on repurchase agreements. The payables for cash collateral received are included on our Condensed Consolidated Balance Sheet in accrued expenses and other liabilities. Included in these amounts is noncash collateral where we have been granted the right to sell or pledge the underlying assets. We have not sold or pledged any of the noncash collateral received under these agreements. Balance Sheet Presentation The following table summarizes the amounts of derivative instruments reported on our Condensed Consolidated Balance Sheet . The amounts are presented on a gross basis, are segregated by derivatives that are designated and qualifying as hedging instruments or those that are not, and are further segregated by type of contract within those two categories. Derivative contracts in a receivable and payable position exclude open trade equity on derivatives cleared through central clearing counterparties. Any associated collateral exchanged with our central clearing counterparties are treated as settlements of the derivative exposure, rather than collateral. Such payments are recognized as settlements of the derivatives contracts in a receivable and payable position on our Condensed Consolidated Balance Sheet . Notional amounts are reference amounts from which contractual obligations are derived and are not recorded on the balance sheet. In our view, derivative notional is not an accurate measure of our derivative exposure when viewed in isolation from other factors, such as market rate fluctuations and counterparty credit risk. June 30, 2018 December 31, 2017 Derivative contracts in a Notional amount Derivative contracts in a Notional amount ($ in millions) receivable position payable position receivable position payable position Derivatives designated as accounting hedges Interest rate contracts Swaps $ — $ — $ 28,840 $ — $ — $ 6,915 Foreign exchange contracts Forwards — 1 145 — 1 136 Total derivatives designated as accounting hedges — 1 28,985 — 1 7,051 Derivatives not designated as accounting hedges Interest rate contracts Futures and forwards — — 9 — — 23 Written options 1 62 6,760 1 39 8,327 Purchased options 62 — 6,694 38 — 8,237 Total interest rate risk 63 62 13,463 39 39 16,587 Foreign exchange contracts Futures and forwards — 1 193 — 1 124 Total foreign exchange risk — 1 193 — 1 124 Equity contracts Written options — 1 — — — — Total equity risk — 1 — — — — Total derivatives not designated as accounting hedges 63 64 13,656 39 40 16,711 Total derivatives $ 63 $ 65 $ 42,641 $ 39 $ 41 $ 23,762 The following table presents amounts recorded on our Condensed Consolidated Balance Sheet related to cumulative basis adjustments for fair value hedges. ($ in millions) Carrying amount of the hedged items Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged items Total Discontinued (a) June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 Assets Available-for-sale securities (b) $ 1,435 $ 173 $ (3 ) $ 2 $ (2 ) $ 2 Finance receivables and loans, net (c) 41,383 2,305 (40 ) 18 11 19 Liabilities Long-term debt $ 14,959 $ 14,640 $ 99 $ 208 $ 95 $ 235 (a) Represents the fair value hedging adjustment on qualifying hedges for which the hedging relationship was discontinued. This represents a subset of the amounts reported in the total hedging adjustment. (b) The carrying amount of hedged available-for-sale securities is presented above using amortized cost. Refer to Note 6 for a reconciliation of the amortized cost and fair value of available-for-sale securities. (c) The hedged item represents the carrying value of the hedged portfolio of assets. The amount that is identified as the last of layer in the hedge relationship is $17.7 billion as of June 30, 2018 . The basis adjustment associated with the last-of-layer relationship is a $51 million liability as of June 30, 2018 , which would be allocated across the entire remaining closed pool upon termination or maturity of the hedge relationship. A last-of-layer hedge strategy did not exist at December 31, 2017 . Statement of Comprehensive Income Presentation The following table summarizes the location and amounts of gains and losses on derivative instruments not designated as accounting hedges reported in our Condensed Consolidated Statement of Comprehensive Income . Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Gain (loss) recognized in earnings Interest rate contracts Gain on mortgage and automotive loans, net $ — $ 1 $ — $ 1 Other income, net of losses (2 ) (1 ) — (3 ) Total interest rate contracts (2 ) — — (2 ) Foreign exchange contracts Other income, net of losses 6 (3 ) 6 (4 ) Total foreign exchange contracts 6 (3 ) 6 (4 ) Gain (loss) recognized in earnings $ 4 $ (3 ) $ 6 $ (6 ) The following table summarizes the location and amounts of gains and losses on derivative instruments designated as fair value hedges reported in our Condensed Consolidated Statement of Comprehensive Income . We had no gains or losses on derivative instruments designated as cash flow hedges for the periods shown. Interest and fees on finance receivables and loans Interest and dividends on investment securities and other earning assets Interest on long-term debt Three months ended June 30, ($ in millions) 2018 2017 2018 2017 2018 2017 Gain (loss) on fair value hedging relationships Interest rate contracts Hedged fixed-rate unsecured debt $ — $ — $ — $ — $ 8 $ (21 ) Derivatives designated as hedging instruments on fixed-rate unsecured debt — — — — (8 ) 21 Hedged fixed-rate FHLB advances — — — — 10 1 Derivatives designated as hedging instruments on fixed-rate FHLB advances — — — — (10 ) (1 ) Hedged available-for-sale securities — — (2 ) 2 — — Derivatives designated as hedging instruments on available-for-sale securities — — 2 (2 ) — — Hedged fixed-rate retail automotive loans (6 ) 1 — — — — Derivatives designated as hedging instruments on fixed-rate retail automotive loans 6 (1 ) — — — — Total loss on fair value hedging relationships $ — $ — $ — $ — $ — $ — Total amounts presented in the Condensed Consolidated Statement of Comprehensive Income $ 1,647 $ 1,447 $ 188 $ 146 $ 434 $ 417 Interest and fees on finance receivables and loans Interest and dividends on investment securities and other earning assets Interest on long-term debt Six months ended June 30, ($ in millions) 2018 2017 2018 2017 2018 2017 Gain (loss) on fair value hedging relationships Interest rate contracts Hedged fixed-rate unsecured debt $ — $ — $ — $ — $ 44 $ (23 ) Derivatives designated as hedging instruments on fixed-rate unsecured debt — — — — (43 ) 24 Hedged fixed-rate FHLB advances — — — — 43 — Derivatives designated as hedging instruments on fixed-rate FHLB advances — — — — (43 ) — Hedged available-for-sale securities — — (5 ) 2 — — Derivatives designated as hedging instruments on available-for-sale securities — — 5 (2 ) — — Hedged fixed-rate retail automotive loans (51 ) (3 ) — — — — Derivatives designated as hedging instruments on fixed-rate retail automotive loans 51 1 — — — — Total (loss) gain on fair value hedging relationships $ — $ (2 ) $ — $ — $ 1 $ 1 Total amounts presented in the Condensed Consolidated Statement of Comprehensive Income $ 3,190 $ 2,815 $ 364 $ 280 $ 845 $ 841 The following table summarizes the location and amounts of gains and losses related to interest and amortization on derivative instruments designated as fair value and cash flow hedges reported in our Condensed Consolidated Statement of Comprehensive Income . Interest and fees on finance receivables and loans Interest on long-term debt Three months ended June 30, ($ in millions) 2018 2017 2018 2017 Gain (loss) on fair value hedging relationships Interest rate contracts Amortization of deferred unsecured debt basis adjustments $ — $ — $ 14 $ 20 Interest for qualifying accounting hedges of unsecured debt — — 1 7 Amortization of deferred secured debt basis adjustments (FHLB advances) — — (5 ) — Interest for qualifying accounting hedges of secured debt (FHLB advances) — — 2 — Amortization of deferred loan basis adjustments (4 ) (6 ) — — Interest for qualifying accounting hedges of retail automotive loans held-for-investment 5 — — — Total (loss) gain on fair value hedging relationships 1 (6 ) 12 27 Gain on cash flow hedging relationships Interest rate contracts Interest for qualifying accounting hedges of variable-rate borrowings — — 2 — Total gain on cash flow hedging relationships $ — $ — $ 2 $ — Interest and fees on finance receivables and loans Interest and dividends on investment securities and other earning assets Interest on long-term debt Six months ended June 30, ($ in millions) 2018 2017 2018 2017 2018 2017 Gain (loss) on fair value hedging relationships Interest rate contracts Amortization of deferred unsecured debt basis adjustments $ — $ — $ — $ — $ 29 $ 40 Interest for qualifying accounting hedges of unsecured debt — — — — 4 12 Amortization of deferred secured debt basis adjustments (FHLB advances) — — — — (6 ) (1 ) Interest for qualifying accounting hedges of secured debt (FHLB advances) — — — — 4 — Interest for qualifying accounting hedges of available-for-sale securities — — (1 ) — — — Amortization of deferred loan basis adjustments (8 ) (11 ) — — — — Interest for qualifying accounting hedges of retail automotive loans held-for-investment (2 ) (1 ) — — — — Total (loss) gain on fair value hedging relationships (10 ) (12 ) (1 ) — 31 51 Gain on cash flow hedging relationships Interest rate contracts Interest for qualifying accounting hedges of variable-rate borrowings — — — — 3 — Total gain on cash flow hedging relationships $ — $ — $ — $ — $ 3 $ — During the next twelve months, we estimate $18 million will be reclassified into pretax earnings from derivatives designated as cash flow hedges. The following table summarizes the effect of cash flow hedges on accumulated other comprehensive loss. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Interest rate contracts Gain recognized in other comprehensive loss $ 5 $ 1 $ 23 $ 1 The following table summarizes the effect of net investment hedges on accumulated other comprehensive loss and the Condensed Consolidated Statement of Comprehensive Income . Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Foreign exchange contracts (a) (b) Gain (loss) recognized in other comprehensive loss $ 3 $ (4 ) $ 7 $ (6 ) (a) There were no amounts excluded from effectiveness testing for the three months and six months ended June 30, 2018 , or 2017 . (b) Gains and losses reclassified from accumulated other comprehensive loss are reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income . There were no amounts reclassified for the three months and six months ended June 30, 2018 , or 2017 .

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	Income Taxes We recognized total income tax expense from continuing operations of $113 million and $189 million for the three months and six months ended June 30, 2018 , respectively, compared to $122 million and $235 million for the same periods in 2017 . The decreases in income tax expense for the three months and six months ended June 30, 2018 , compared to the same periods in 2017 , were primarily driven by the reduction of the U.S. federal corporate tax rate enacted as a result of the Tax Act. This decrease was partially offset by an increase in pretax earnings, nondeductible FDIC premiums as a result of the Tax Act, and a nonrecurring tax benefit in 2017 from the release of valuation allowance against our capital-in-nature deferred tax assets and foreign tax credit carryforwards. As further described in Note 1 , we elected to early-adopt ASU 2018-02 effective January 1, 2018. As a result of this adoption, we reclassified $42 million from accumulated other comprehensive loss to retained earnings, which eliminated the stranded federal income tax effects in accumulated other comprehensive loss resulting from the Tax Act. Our policy is to use the portfolio method with respect to reclassification of stranded income tax effects in accumulated other comprehensive loss. 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 credit carryforwards, state net operating loss carryforwards, and state capital 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 these carryforwards.

Fair Value

Fair Value	6 Months Ended
	Jun. 30, 2018
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. There were no transfers between any levels for the six months ended June 30, 2018. The 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. • Equity Securities — Includes various marketable equity securities measured at fair value with changes in fair value recognized in net income. Measurements based on observable market prices are classified as Level 1. • 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, caps, floors, and agency to-be-announced securities. We utilize third-party-developed valuation models that are widely accepted in the market to value these 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 derivative contracts as Level 2 because all significant inputs into these models were market observable. We also enter into interest rate lock commitments and forward-sale commitments that are executed as part of our mortgage business, certain of which 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 with unobservable inputs, 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 June 30, 2018 ($ in millions) Level 1 Level 2 Level 3 Total Assets Investment securities Equity securities (a) $ 509 $ — $ 12 $ 521 Available-for-sale securities Debt securities U.S. Treasury 1,874 — — 1,874 U.S. States and political subdivisions — 851 — 851 Foreign government 7 147 — 154 Agency mortgage-backed residential — 15,066 — 15,066 Mortgage-backed residential — 2,625 — 2,625 Mortgage-backed commercial — 642 — 642 Asset-backed — 868 — 868 Corporate debt — 1,216 — 1,216 Total available-for-sale securities 1,881 21,415 — 23,296 Mortgage loans held-for-sale (b) — — 13 13 Interests retained in financial asset sales — — 4 4 Derivative contracts in a receivable position Interest rate — 62 1 63 Total derivative contracts in a receivable position — 62 1 63 Total assets $ 2,390 $ 21,477 $ 30 $ 23,897 Liabilities Accrued expenses and other liabilities Derivative contracts in a payable position Interest rate $ — $ 62 $ — $ 62 Foreign currency — 2 — 2 Other 1 — — 1 Total derivative contracts in a payable position 1 64 — 65 Total liabilities $ 1 $ 64 $ — $ 65 (a) Our investment in any one industry did not exceed 15% . (b) Carried at fair value due to fair value option elections. Recurring fair value measurements December 31, 2017 ($ in millions) Level 1 Level 2 Level 3 Total Assets Investment securities Equity securities (a) $ 518 $ — $ — $ 518 Available-for-sale securities Debt securities U.S. Treasury 1,777 — — 1,777 U.S. States and political subdivisions — 854 — 854 Foreign government 8 146 — 154 Agency mortgage-backed residential — 14,291 — 14,291 Mortgage-backed residential — 2,494 — 2,494 Mortgage-backed commercial — 541 — 541 Asset-backed — 936 — 936 Corporate debt — 1,256 — 1,256 Total available-for-sale securities 1,785 20,518 — 22,303 Mortgage loans held-for-sale (b) — — 13 13 Interests retained in financial asset sales — — 5 5 Derivative contracts in a receivable position Interest rate — 38 1 39 Total derivative contracts in a receivable position — 38 1 39 Total assets $ 2,303 $ 20,556 $ 19 $ 22,878 Liabilities Accrued expenses and other liabilities Derivative contracts in a payable position Interest rate $ — $ 39 $ — $ 39 Foreign currency — 2 — 2 Total derivative contracts in a payable position — 41 — 41 Total liabilities $ — $ 41 $ — $ 41 (a) Our investment in any one industry did not exceed 14% . (b) Carried at fair value due to fair value option elections. 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 June 30, 2018 Net unrealized gains included in earnings still held at June 30, 2018 ($ in millions) Fair value at April 1, 2018 included in earnings included in OCI Purchases Sales Issuances Settlements Assets Equity securities $ 12 $ — $ — $ — $ — $ — $ — $ 12 $ — Mortgage loans held-for-sale (a) 7 1 (b) — 73 (68 ) — — 13 — Other assets Interests retained in financial asset sales 5 — — — — — (1 ) 4 — Derivative assets 1 — — — — — — 1 — Total assets $ 25 $ 1 $ — $ 73 $ (68 ) $ — $ (1 ) $ 30 $ — (a) Carried at fair value due to fair value option elections. (b) Reported as gain on mortgage and automotive loans, net, in the Condensed Consolidated Statement of Comprehensive Income . Level 3 recurring fair value measurements Fair value at April 1, 2017 Net realized/unrealized gains Purchases Sales Issuances Settlements Fair value at June 30, 2017 Net unrealized gains included in earnings still held at June 30, 2017 ($ in millions) included in earnings included in OCI Assets Mortgage loans held-for-sale (a) $ 1 $ — $ — $ 20 $ (18 ) $ — $ — $ 3 $ — Other assets Interests retained in financial asset sales 31 1 (b) — — 4 — (31 ) 5 — Derivative assets — 1 (c) — — — — — 1 1 Total assets $ 32 $ 2 $ — $ 20 $ (14 ) $ — $ (31 ) $ 9 $ 1 (a) Carried at fair value due to fair value option elections. (b) Reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income . (c) Reported as gain on mortgage and automotive loans, net, in the Condensed Consolidated Statement of Comprehensive Income . Level 3 recurring fair value measurements Net realized/unrealized (losses) gains Fair value at June 30, 2018 Net unrealized losses included in earnings still held at June 30, 2018 ($ in millions) Fair value at Jan. 1, 2018 included in earnings included in OCI Purchases Sales Issuances Settlements Assets Equity securities (a) $ 19 $ (4 ) (b) $ — $ — $ — $ — $ (3 ) $ 12 $ (5 ) Mortgage loans held-for-sale (c) 13 2 (d) — 132 (134 ) — — 13 — Other assets Interests retained in financial asset sales 5 — — — — — (1 ) 4 — Derivative assets 1 — — — — — — 1 — Total assets $ 38 $ (2 ) $ — $ 132 $ (134 ) $ — $ (4 ) $ 30 $ (5 ) (a) In connection with our adoption of ASU 2016-01 on January 1, 2018, certain of our equity securities previously measured using the cost method of accounting are now measured at fair value on a recurring basis, and have been categorized as Level 3 within the fair value hierarchy. Accordingly, the fair value of such investments has been included in the opening balance of the reconciliation above. (b) Reported as other loss on investments, net, in the Condensed Consolidated Statement of Comprehensive Income . (c) Carried at fair value due to fair value option elections. (d) Reported as gain on mortgage and automotive loans, net, in the Condensed Consolidated Statement of Comprehensive Income . Level 3 recurring fair value measurements Fair value at Jan. 1, 2017 Net realized/unrealized gains Purchases Sales Issuances Settlements Fair value at June 30, 2017 Net unrealized gains included in earnings still held at June 30, 2017 ($ in millions) included in earnings included in OCI Assets Mortgage loans held-for-sale (a) $ — $ — $ — $ 23 $ (20 ) $ — $ — $ 3 $ — Other assets Interests retained in financial asset sales 29 1 (b) — — 8 — (33 ) 5 — Derivative assets — 1 (c) — — — — — 1 1 Total assets $ 29 $ 2 $ — $ 23 $ (12 ) $ — $ (33 ) $ 9 $ 1 (a) Carried at fair value due to fair value option elections. (b) Reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income . (c) Reported as gain on mortgage and automotive loans, net, 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 June 30, 2018 ($ in millions) Level 1 Level 2 Level 3 Total Assets Loans held-for-sale, net $ — $ — $ 315 $ 315 $ — n/m (a) Commercial finance receivables and loans, net (b) Automotive — — 62 62 (12 ) n/m (a) Other — — 50 50 (15 ) n/m (a) Total commercial finance receivables and loans, net — — 112 112 (27 ) n/m (a) Other assets Repossessed and foreclosed assets (c) — — 13 13 (1 ) n/m (a) Total assets $ — $ — $ 440 $ 440 $ (28 ) 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 2018 . 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 (loss) included in earnings December 31, 2017 ($ in millions) Level 1 Level 2 Level 3 Total Assets Loans held-for-sale, net $ — $ — $ 77 $ 77 $ — n/m (a) Commercial finance receivables and loans, net (b) Automotive — — 20 20 (3 ) n/m (a) Other — — 22 22 (12 ) n/m (a) Total commercial finance receivables and loans, net — — 42 42 (15 ) n/m (a) Other assets Repossessed and foreclosed assets (c) — — 14 14 (1 ) n/m (a) Other — — 3 3 — n/m (a) Total assets $ — $ — $ 136 $ 136 $ (16 ) 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. 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 derivatives. Our intent in electing fair value measurement was to mitigate a divergence between accounting gains or 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 June 30, 2018 , and December 31, 2017 . Estimated fair value ($ in millions) Carrying value Level 1 Level 2 Level 3 Total June 30, 2018 Financial assets Held-to-maturity securities $ 2,089 $ — $ 2,007 $ — $ 2,007 Loans held-for-sale, net 315 — — 315 315 Finance receivables and loans, net 124,287 — — 125,846 125,846 Nonmarketable equity investments 1,237 — 1,237 — 1,237 Financial liabilities Deposit liabilities (a) $ 49,617 $ — $ — $ 49,493 $ 49,493 Short-term borrowings 7,108 — — 7,112 7,112 Long-term debt 47,328 — 28,040 21,094 49,134 December 31, 2017 Financial assets Held-to-maturity securities $ 1,899 $ — $ 1,865 $ — $ 1,865 Loans held-for-sale, net 95 — — 95 95 Finance receivables and loans, net 121,617 — — 123,302 123,302 Nonmarketable equity investments 1,233 — 1,190 49 1,239 Financial liabilities Deposit liabilities (a) $ 45,869 $ — $ — $ 45,827 $ 45,827 Short-term borrowings 11,413 — — 11,417 11,417 Long-term debt 44,226 — 27,807 18,817 46,624 (a) In connection with our adoption of ASU 2016-01 on January 1, 2018, deposit liabilities with no defined or contractual maturities are no longer included in the table above. Amounts for December 31, 2017, have been adjusted to conform to the current presentation and exclude $47.4 billion and $45.2 billion of deposit liabilities with no defined or contractual maturities from the carrying value and Level 3 fair value, respectively. Refer to Note 12 for information regarding the composition of our deposits portfolio, and Note 1 for further information regarding recently adopted accounting standards.

Offsetting Assets and Liabiliti

Offsetting Assets and Liabilities	6 Months Ended
	Jun. 30, 2018
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 (i) 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 (ii) 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 June 30, 2018 , 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 on the Condensed Consolidated Balance Sheet Net amounts of assets/liabilities presented on the Condensed Consolidated Balance Sheet Gross amounts not offset on the Condensed Consolidated Balance Sheet June 30, 2018 ($ in millions) Financial instruments Collateral (a) (b) (c) Net amount Assets Derivative assets in net asset positions $ 62 $ — $ 62 $ — $ — $ 62 Derivative assets with no offsetting arrangements 1 — 1 — — 1 Total assets (d) $ 63 $ — $ 63 $ — $ — $ 63 Liabilities Derivative liabilities in net liability positions (d) $ 65 $ — $ 65 $ — $ (1 ) $ 64 Securities sold under agreements to repurchase (e) 967 — 967 — (967 ) — Total liabilities $ 1,032 $ — $ 1,032 $ — $ (968 ) $ 64 (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. $11 million of noncash derivative collateral pledged to us was excluded at June 30, 2018 . 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 $11 million at June 30, 2018 . We have not sold or pledged any of the noncash collateral received under these agreements as of June 30, 2018 . (d) For additional information on derivative instruments and hedging activities, refer to Note 18 . (e) For additional information on securities sold under agreements to repurchase, refer to Note 13 . Gross amounts of recognized assets/liabilities Gross amounts offset on the Condensed Consolidated Balance Sheet Net amounts of assets/liabilities presented on the Condensed Consolidated Balance Sheet Gross amounts not offset on the Condensed Consolidated Balance Sheet December 31, 2017 ($ in millions) Financial instruments Collateral (a) (b) (c) Net amount Assets Derivative assets in net asset positions $ 38 $ — $ 38 $ — $ — $ 38 Derivative assets with no offsetting arrangements 1 — 1 — — 1 Total assets (d) $ 39 $ — $ 39 $ — $ — $ 39 Liabilities Derivative liabilities in net liability positions (d) $ 41 $ — $ 41 $ — $ (1 ) $ 40 Securities sold under agreements to repurchase (e) 892 — 892 — (892 ) — Total liabilities $ 933 $ — $ 933 $ — $ (893 ) $ 40 (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 December 31, 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 December 31, 2017. We have not sold or pledged any of the noncash collateral received under these agreements as of December 31, 2017. (d) For additional information on derivative instruments and hedging activities, refer to Note 18 . (e) For additional information on securities sold under agreements to repurchase, refer to Note 13 .

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2018
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 United States providing automotive financing services to consumers, automotive dealers, 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 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 VSCs, VMCs, and GAP 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 with the assistance of a third-party fulfillment partner. Jumbo mortgage loans are generally held on our balance sheet and are accounted for as held-for-investment. Conforming mortgage loans are generally originated as held-for-sale and then sold to the fulfillment partner , and we retain no mortgage servicing rights associated with those loans that are sold. 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 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, original issue discount, 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 June 30, ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated (a) 2018 Net financing revenue and other interest income $ 925 $ 13 $ 44 $ 57 $ 55 $ 1,094 Other revenue 63 266 2 14 19 364 Total net revenue 988 279 46 71 74 1,458 Provision for loan losses 170 — — (6 ) (6 ) 158 Total noninterest expense 436 268 32 19 84 839 Income (loss) from continuing operations before income tax expense $ 382 $ 11 $ 14 $ 58 $ (4 ) $ 461 Total assets $ 114,915 $ 7,634 $ 13,385 $ 4,458 $ 30,953 $ 171,345 2017 Net financing revenue and other interest income $ 932 $ 14 $ 32 $ 48 $ 41 $ 1,067 Other revenue 107 245 1 10 25 388 Total net revenue 1,039 259 33 58 66 1,455 Provision for loan losses 266 — 1 6 (4 ) 269 Total noninterest expense 426 280 25 17 62 810 Income (loss) from continuing operations before income tax expense $ 347 $ (21 ) $ 7 $ 35 $ 8 $ 376 Total assets $ 115,447 $ 7,308 $ 8,902 $ 3,552 $ 29,136 $ 164,345 (a) Net financing revenue and other interest income after the provision for loan losses totaled $936 million and $798 million for the three months ended June 30, 2018 , and 2017, respectively. Six months ended June 30, ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated (a) 2018 Net financing revenue and other interest income $ 1,834 $ 25 $ 87 $ 103 $ 94 $ 2,143 Other revenue 129 512 3 22 52 718 Total net revenue 1,963 537 90 125 146 2,861 Provision for loan losses 429 — 2 (6 ) (6 ) 419 Total noninterest expense 884 499 66 44 160 1,653 Income (loss) from continuing operations before income tax expense $ 650 $ 38 $ 22 $ 87 $ (8 ) $ 789 Total assets $ 114,915 $ 7,634 $ 13,385 $ 4,458 $ 30,953 $ 171,345 2017 Net financing revenue and other interest income $ 1,824 $ 29 $ 66 $ 82 $ 45 $ 2,046 Other revenue 208 509 1 28 38 784 Total net revenue 2,032 538 67 110 83 2,830 Provision for loan losses 534 — 2 12 (8 ) 540 Total noninterest expense 863 519 49 38 119 1,588 Income (loss) from continuing operations before income tax expense $ 635 $ 19 $ 16 $ 60 $ (28 ) $ 702 Total assets $ 115,447 $ 7,308 $ 8,902 $ 3,552 $ 29,136 $ 164,345 (a) Net financing revenue and other interest income after the provision for loan losses totaled $1.7 billion and $1.5 billion for the six months ended June 30, 2018 , and 2017, respectively.

Parent and Guarantor Condensed

Parent and Guarantor Condensed Consolidating Financial Statements	6 Months Ended
	Jun. 30, 2018
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 June 30, 2018 , 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 June 30, 2018 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing revenue and other interest income Interest and fees on finance receivables and loans $ (1 ) $ — $ 1,648 $ — $ 1,647 Interest and fees on finance receivables and loans — intercompany 4 — 1 (5 ) — Interest on loans held-for-sale — — 6 — 6 Interest and dividends on investment securities and other earning assets — — 188 — 188 Interest on cash and cash equivalents 2 — 14 1 17 Interest-bearing cash — intercompany 2 — 2 (4 ) — Operating leases 1 — 373 — 374 Total financing revenue and other interest income 8 — 2,232 (8 ) 2,232 Interest expense Interest on deposits — — 395 4 399 Interest on short-term borrowings 10 — 30 — 40 Interest on long-term debt 257 — 177 — 434 Interest on intercompany debt 4 — 8 (12 ) — Total interest expense 271 — 610 (8 ) 873 Net depreciation expense on operating lease assets 1 — 264 — 265 Net financing (loss) revenue (264 ) — 1,358 — 1,094 Cash dividends from subsidiaries Bank subsidiary 500 500 — (1,000 ) — Nonbank subsidiaries 132 — — (132 ) — Other revenue Insurance premiums and service revenue earned — — 239 — 239 Gain on mortgage and automotive loans, net — — 1 — 1 Other gain on investments, net — — 27 — 27 Other income, net of losses 100 — 185 (188 ) 97 Total other revenue 100 — 452 (188 ) 364 Total net revenue 468 500 1,810 (1,320 ) 1,458 Provision for loan losses 32 — 126 — 158 Noninterest expense Compensation and benefits expense 25 — 267 — 292 Insurance losses and loss adjustment expenses — — 101 — 101 Other operating expenses 173 — 461 (188 ) 446 Total noninterest expense 198 — 829 (188 ) 839 Income from continuing operations before income tax (benefit) expense and undistributed income (loss) of subsidiaries 238 500 855 (1,132 ) 461 Income tax (benefit) expense from continuing operations (66 ) — 179 — 113 Net income from continuing operations 304 500 676 (1,132 ) 348 (Loss) income from discontinued operations, net of tax (1 ) — 2 — 1 Undistributed income (loss) of subsidiaries Bank subsidiary 52 52 — (104 ) — Nonbank subsidiaries (6 ) — — 6 — Net income 349 552 678 (1,230 ) 349 Other comprehensive loss, net of tax (70 ) (56 ) (74 ) 130 (70 ) Comprehensive income $ 279 $ 496 $ 604 $ (1,100 ) $ 279 Three months ended June 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 $ (35 ) $ — $ 1,482 $ — $ 1,447 Interest and fees on finance receivables and loans — intercompany 3 — 2 (5 ) — Interest and dividends on investment securities and other earning assets — — 146 — 146 Interest on cash and cash equivalents 2 — 5 — 7 Interest-bearing cash — intercompany — — 2 (2 ) — Operating leases 3 — 485 — 488 Total financing (loss) revenue and other interest income (27 ) — 2,122 (7 ) 2,088 Interest expense Interest on deposits 1 — 249 — 250 Interest on short-term borrowings 19 — 14 — 33 Interest on long-term debt 274 — 143 — 417 Interest on intercompany debt 4 — 3 (7 ) — Total interest expense 298 — 409 (7 ) 700 Net depreciation expense on operating lease assets 3 — 318 — 321 Net financing (loss) revenue (328 ) — 1,395 — 1,067 Cash dividends from subsidiaries Nonbank subsidiaries 387 — — (387 ) — Other revenue Insurance premiums and service revenue earned — — 227 — 227 Gain on mortgage and automotive loans, net 32 — 4 — 36 Other gain on investments, net — — 23 — 23 Other income, net of losses 163 — 210 (271 ) 102 Total other revenue 195 — 464 (271 ) 388 Total net revenue 254 — 1,859 (658 ) 1,455 Provision for loan losses 82 — 187 — 269 Noninterest expense Compensation and benefits expense 19 — 246 — 265 Insurance losses and loss adjustment expenses — — 125 — 125 Other operating expenses 213 — 478 (271 ) 420 Total noninterest expense 232 — 849 (271 ) 810 (Loss) income from continuing operations before income tax (benefit) expense and undistributed income (loss) of subsidiaries (60 ) — 823 (387 ) 376 Income tax (benefit) expense from continuing operations (93 ) — 215 — 122 Net income from continuing operations 33 — 608 (387 ) 254 Loss from discontinued operations, net of tax — — (2 ) — (2 ) Undistributed income (loss) of subsidiaries Bank subsidiary 375 375 — (750 ) — Nonbank subsidiaries (156 ) — — 156 — Net income 252 375 606 (981 ) 252 Other comprehensive income, net of tax 76 50 72 (122 ) 76 Comprehensive income $ 328 $ 425 $ 678 $ (1,103 ) $ 328 Six months ended June 30, 2018 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing revenue and other interest income Interest and fees on finance receivables and loans $ 10 $ — $ 3,180 $ — $ 3,190 Interest and fees on finance receivables and loans — intercompany 6 — 2 (8 ) — Interest on loans held-for-sale — — 6 — 6 Interest and dividends on investment securities and other earning assets — — 365 (1 ) 364 Interest on cash and cash equivalents 4 — 28 — 32 Interest-bearing cash — intercompany 4 — 4 (8 ) — Operating leases 3 — 753 — 756 Total financing revenue and other interest income 27 — 4,338 (17 ) 4,348 Interest expense Interest on deposits — — 750 — 750 Interest on short-term borrowings 20 — 52 — 72 Interest on long-term debt 515 — 330 — 845 Interest on intercompany debt 7 — 10 (17 ) — Total interest expense 542 — 1,142 (17 ) 1,667 Net depreciation expense on operating lease assets 5 — 533 — 538 Net financing (loss) revenue (520 ) — 2,663 — 2,143 Cash dividends from subsidiaries Bank subsidiary 1,500 1,500 — (3,000 ) — Nonbank subsidiaries 301 — — (301 ) — Other revenue Insurance premiums and service revenue earned — — 495 — 495 Gain on mortgage and automotive loans, net 28 — 2 (28 ) 2 Other gain on investments, net — — 15 — 15 Other income, net of losses 196 — 406 (396 ) 206 Total other revenue 224 — 918 (424 ) 718 Total net revenue 1,505 1,500 3,581 (3,725 ) 2,861 Provision for loan losses 113 — 334 (28 ) 419 Noninterest expense Compensation and benefits expense 48 — 550 — 598 Insurance losses and loss adjustment expenses — — 164 — 164 Other operating expenses 355 — 932 (396 ) 891 Total noninterest expense 403 — 1,646 (396 ) 1,653 Income from continuing operations before income tax (benefit) expense and undistributed (loss) income of subsidiaries 989 1,500 1,601 (3,301 ) 789 Income tax (benefit) expense from continuing operations (122 ) — 311 — 189 Net income from continuing operations 1,111 1,500 1,290 (3,301 ) 600 (Loss) income from discontinued operations, net of tax (2 ) — 1 — (1 ) Undistributed (loss) income of subsidiaries Bank subsidiary (545 ) (545 ) — 1,090 — Nonbank subsidiaries 35 — — (35 ) — Net income 599 955 1,291 (2,246 ) 599 Other comprehensive loss, net of tax (398 ) (332 ) (413 ) 745 (398 ) Comprehensive income $ 201 $ 623 $ 878 $ (1,501 ) $ 201 Six months ended June 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 $ (70 ) $ — $ 2,885 $ — $ 2,815 Interest and fees on finance receivables and loans — intercompany 7 — 4 (11 ) — Interest and dividends on investment securities and other earning assets — — 281 (1 ) 280 Interest on cash and cash equivalents 4 — 8 — 12 Interest-bearing cash — intercompany — — 3 (3 ) — Operating leases 6 — 1,025 — 1,031 Total financing (loss) revenue and other interest income (53 ) — 4,206 (15 ) 4,138 Interest expense Interest on deposits 2 — 479 — 481 Interest on short-term borrowings 36 — 24 — 60 Interest on long-term debt 556 — 285 — 841 Interest on intercompany debt 8 — 7 (15 ) — Total interest expense 602 — 795 (15 ) 1,382 Net depreciation expense on operating lease assets 5 — 705 — 710 Net financing (loss) revenue (660 ) — 2,706 — 2,046 Cash dividends from subsidiaries Nonbank subsidiaries 427 — — (427 ) — Other revenue Insurance premiums and service revenue earned — — 468 — 468 Gain on mortgage and automotive loans, net 30 — 20 — 50 Other gain on investments, net — — 50 — 50 Other income, net of losses 431 — 433 (648 ) 216 Total other revenue 461 — 971 (648 ) 784 Total net revenue 228 — 3,677 (1,075 ) 2,830 Provision for loan losses 189 — 351 — 540 Noninterest expense Compensation and benefits expense 140 — 410 — 550 Insurance losses and loss adjustment expenses — — 213 — 213 Other operating expenses 501 — 972 (648 ) 825 Total noninterest expense 641 — 1,595 (648 ) 1,588 (Loss) income from continuing operations before income tax (benefit) expense and undistributed income of subsidiaries (602 ) — 1,731 (427 ) 702 Income tax (benefit) expense from continuing operations (227 ) — 462 — 235 Net (loss) income from continuing operations (375 ) — 1,269 (427 ) 467 Income (loss) from discontinued operations, net of tax 2 — (3 ) — (1 ) Undistributed income of subsidiaries Bank subsidiary 764 764 — (1,528 ) — Nonbank subsidiaries 75 — — (75 ) — Net income 466 764 1,266 (2,030 ) 466 Other comprehensive income, net of tax 96 55 91 (146 ) 96 Comprehensive income $ 562 $ 819 $ 1,357 $ (2,176 ) $ 562 Condensed Consolidating Balance Sheet June 30, 2018 ($ in millions) Parent (a) Guarantors Nonguarantors (a) Consolidating adjustments Ally consolidated Assets Cash and cash equivalents Noninterest-bearing $ 49 $ — $ 750 $ — $ 799 Interest-bearing 6 — 3,119 — 3,125 Interest-bearing — intercompany 1,016 — 569 (1,585 ) — Total cash and cash equivalents 1,071 — 4,438 (1,585 ) 3,924 Equity securities — — 521 — 521 Available-for-sale securities — — 23,296 — 23,296 Held-to-maturity securities — — 2,146 (57 ) 2,089 Loans held-for-sale, net — — 328 — 328 Finance receivables and loans, net Finance receivables and loans, net 5,647 — 119,897 — 125,544 Intercompany loans to Nonbank subsidiaries 786 — 405 (1,191 ) — Allowance for loan losses (128 ) — (1,129 ) — (1,257 ) Total finance receivables and loans, net 6,305 — 119,173 (1,191 ) 124,287 Investment in operating leases, net 10 — 8,629 — 8,639 Intercompany receivables from Bank subsidiary 106 — — (106 ) — Nonbank subsidiaries 61 — 88 (149 ) — Investment in subsidiaries Bank subsidiary 16,163 16,163 — (32,326 ) — Nonbank subsidiaries 7,162 — — (7,162 ) — Premiums receivable and other insurance assets — — 2,247 — 2,247 Other assets 2,123 — 5,129 (1,238 ) 6,014 Total assets $ 33,001 $ 16,163 $ 165,995 $ (43,814 ) $ 171,345 Liabilities Deposit liabilities Noninterest-bearing $ — $ — $ 153 $ — $ 153 Interest-bearing 6 — 98,575 — 98,581 Interest-bearing — intercompany — — 1,016 (1,016 ) — Total deposit liabilities 6 — 99,744 (1,016 ) 98,734 Short-term borrowings 2,666 — 4,442 — 7,108 Long-term debt 15,571 — 31,757 — 47,328 Intercompany debt to Bank subsidiary 57 — — (57 ) — Nonbank subsidiaries 973 — 786 (1,759 ) — Intercompany payables to Nonbank subsidiaries 130 — 129 (259 ) — Interest payable 192 — 376 — 568 Unearned insurance premiums and service revenue — — 2,957 — 2,957 Accrued expenses and other liabilities 267 — 2,479 (1,235 ) 1,511 Total liabilities 19,862 — 142,670 (4,326 ) 158,206 Total equity 13,139 16,163 23,325 (39,488 ) 13,139 Total liabilities and equity $ 33,001 $ 16,163 $ 165,995 $ (43,814 ) $ 171,345 (a) Amounts presented are based upon the legal transfer of the underlying assets to VIEs in order to reflect legal ownership. December 31, 2017 ($ in millions) Parent (a) Guarantors Nonguarantors (a) Consolidating adjustments Ally consolidated Assets Cash and cash equivalents Noninterest-bearing $ 74 $ — $ 770 $ — $ 844 Interest-bearing 5 — 3,403 — 3,408 Interest-bearing — intercompany 1,138 — 695 (1,833 ) — Total cash and cash equivalents 1,217 — 4,868 (1,833 ) 4,252 Equity securities — — 518 — 518 Available-for-sale securities — — 22,303 — 22,303 Held-to-maturity securities — — 1,973 (74 ) 1,899 Loans held-for-sale, net — — 108 — 108 Finance receivables and loans, net Finance receivables and loans, net 7,434 — 115,459 — 122,893 Intercompany loans to Nonbank subsidiaries 879 — 408 (1,287 ) — Allowance for loan losses (185 ) — (1,091 ) — (1,276 ) Total finance receivables and loans, net 8,128 — 114,776 (1,287 ) 121,617 Investment in operating leases, net 19 — 8,722 — 8,741 Intercompany receivables from Bank subsidiary 80 — — (80 ) — Nonbank subsidiaries 71 — 77 (148 ) — Investment in subsidiaries Bank subsidiary 16,962 16,962 — (33,924 ) — Nonbank subsidiaries 8,111 — — (8,111 ) — Premiums receivable and other insurance assets — — 2,082 (35 ) 2,047 Other assets 2,207 — 5,105 (1,649 ) 5,663 Total assets $ 36,795 $ 16,962 $ 160,532 $ (47,141 ) $ 167,148 Liabilities Deposit liabilities Noninterest-bearing $ — $ — $ 108 $ — $ 108 Interest-bearing 12 — 93,136 — 93,148 Interest-bearing — intercompany — — 1,139 (1,139 ) — Total deposit liabilities 12 — 94,383 (1,139 ) 93,256 Short-term borrowings 3,171 — 8,242 — 11,413 Long-term debt 17,966 — 26,260 — 44,226 Intercompany debt to Bank subsidiary 74 — — (74 ) — Nonbank subsidiaries 1,103 — 879 (1,982 ) — Intercompany payables to Bank subsidiary 4 — — (4 ) — Nonbank subsidiaries 132 — 127 (259 ) — Interest payable 200 — 175 — 375 Unearned insurance premiums and service revenue — — 2,604 — 2,604 Accrued expenses and other liabilities 639 — 2,790 (1,649 ) 1,780 Total liabilities 23,301 — 135,460 (5,107 ) 153,654 Total equity 13,494 16,962 25,072 (42,034 ) 13,494 Total liabilities and equity $ 36,795 $ 16,962 $ 160,532 $ (47,141 ) $ 167,148 (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 Six months ended June 30, 2018 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Operating activities Net cash provided by operating activities $ 958 $ 1,500 $ 2,853 $ (3,302 ) $ 2,009 Investing activities Purchases of equity securities — — (500 ) — (500 ) Proceeds from sales of equity securities — — 535 — 535 Purchases of available-for-sale securities — — (4,094 ) — (4,094 ) Proceeds from sales of available-for-sale securities — — 390 — 390 Proceeds from repayments of available-for-sale securities — — 1,621 — 1,621 Purchases of held-to-maturity securities — — (316 ) — (316 ) Proceeds from repayments of held-to-maturity securities — — 72 — 72 Net change in investment securities — intercompany — — 17 (17 ) — Purchases of finance receivables and loans held-for-investment — — (3,431 ) 820 (2,611 ) Proceeds from sales of finance receivables and loans initially held-for-investment 820 — — (820 ) — Originations and repayments of finance receivables and loans held-for-investment and other, net 1,331 — (1,969 ) — (638 ) Net change in loans — intercompany 83 — (5 ) (78 ) — Purchases of operating lease assets — — (2,107 ) — (2,107 ) Disposals of operating lease assets 6 — 1,757 — 1,763 Capital contributions to subsidiaries (57 ) (6 ) — 63 — Returns of contributed capital 194 — — (194 ) — Net change in nonmarketable equity investments — — (46 ) — (46 ) Other, net (3 ) — (183 ) — (186 ) Net cash provided by (used in) investing activities 2,374 (6 ) (8,259 ) (226 ) (6,117 ) Financing activities Net change in short-term borrowings — third party (505 ) — (3,800 ) — (4,305 ) Net (decrease) increase in deposits (6 ) — 5,324 123 5,441 Proceeds from issuance of long-term debt — third party 32 — 12,908 — 12,940 Repayments of long-term debt — third party (2,412 ) — (7,388 ) — (9,800 ) Net change in debt — intercompany (138 ) — (83 ) 221 — Repurchase of common stock (380 ) — — — (380 ) Dividends paid — third party (115 ) — — — (115 ) Dividends paid and returns of contributed capital — intercompany — (1,500 ) (1,995 ) 3,495 — Capital contributions from parent — 6 57 (63 ) — Net cash (used in) provided by financing activities (3,524 ) (1,494 ) 5,023 3,776 3,781 Effect of exchange-rate changes on cash and cash equivalents — — (3 ) — (3 ) Net decrease in cash and cash equivalents and restricted cash (192 ) — (386 ) 248 (330 ) Cash and cash equivalents and restricted cash at beginning of year 1,395 — 5,707 (1,833 ) 5,269 Cash and cash equivalents and restricted cash at June 30, $ 1,203 $ — $ 5,321 $ (1,585 ) $ 4,939 The following table provides a reconciliation of cash and cash equivalents and restricted cash from the Condensed Consolidated Balance Sheet to the Condensed Consolidated Statement of Cash Flows. June 30, 2018 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet $ 1,071 $ — $ 4,438 $ (1,585 ) $ 3,924 Restricted cash included in other assets on the Condensed Consolidated Balance Sheet (a) 132 — 883 — 1,015 Total cash and cash equivalents and restricted cash as disclosed in the Condensed Consolidated Statement of Cash Flows $ 1,203 $ — $ 5,321 $ (1,585 ) $ 4,939 (a) Restricted cash balances relate primarily to Ally securitization arrangements. Refer to Note 11 for additional details describing the nature of restricted cash balances. Six months ended June 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Operating activities Net cash provided by operating activities $ 561 $ — $ 1,856 $ (347 ) $ 2,070 Investing activities Purchases of equity securities — — (363 ) — (363 ) Proceeds from sales of equity securities — — 484 — 484 Purchases of available-for-sale securities — — (5,490 ) — (5,490 ) Proceeds from sales of available-for-sale securities — — 1,678 — 1,678 Proceeds from repayments of available-for-sale securities — — 1,230 — 1,230 Purchases of held-to-maturity securities — — (313 ) — (313 ) Proceeds from repayments of held-to-maturity securities — — 17 — 17 Net change in investment securities — intercompany 1 — 269 (270 ) — Purchases of finance receivables and loans held-for-investment (35 ) — (1,782 ) — (1,817 ) Proceeds from sales of finance receivables and loans initially held-for-investment 67 — 1,213 — 1,280 Originations and repayments of finance receivables and loans held-for-investment and other, net 1,044 — (676 ) (1,956 ) (1,588 ) Net change in loans — intercompany 1,864 — 246 (2,110 ) — Purchases of operating lease assets — — (1,965 ) — (1,965 ) Disposals of operating lease assets 4 — 3,039 — 3,043 Capital contributions to subsidiaries (824 ) — — 824 — Returns of contributed capital 838 — — (838 ) — Net change in nonmarketable equity investments — — 107 — 107 Other, net (21 ) — 27 (96 ) (90 ) Net cash provided by (used in) investing activities 2,938 — (2,279 ) (4,446 ) (3,787 ) Financing activities Net change in short-term borrowings — third party 1,083 — (3,045 ) — (1,962 ) Net (decrease) increase in deposits (123 ) — 7,256 — 7,133 Proceeds from issuance of long-term debt — third party 353 — 7,016 1,961 9,330 Repayments of long-term debt — third party (3,323 ) — (11,043 ) — (14,366 ) Net change in debt — intercompany (370 ) — (1,864 ) 2,234 — Repurchase of common stock (373 ) — — — (373 ) Dividends paid — third party (75 ) — — — (75 ) Dividends paid and returns of contributed capital — intercompany — — (1,266 ) 1,266 — Capital contributions from parent — — 824 (824 ) — Net cash used in financing activities (2,828 ) — (2,122 ) 4,637 (313 ) Effect of exchange-rate changes on cash and cash equivalents — — 2 — 2 Net increase (decrease) in cash and cash equivalents and restricted cash 671 — (2,543 ) (156 ) (2,028 ) Cash and cash equivalents and restricted cash at beginning of year 989 — 7,293 (401 ) 7,881 Cash and cash equivalents and restricted cash at June 30, $ 1,660 $ — $ 4,750 $ (557 ) $ 5,853 The following table provides a reconciliation of cash and cash equivalents and restricted cash from the Condensed Consolidated Balance Sheet to the Condensed Consolidated Statement of Cash Flows. June 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet $ 1,441 $ — $ 3,493 $ (557 ) $ 4,377 Restricted cash included in other assets on the Condensed Consolidated Balance Sheet (a) 219 — 1,257 — 1,476 Total cash and cash equivalents and restricted cash as disclosed in the Condensed Consolidated Statement of Cash Flows $ 1,660 $ — $ 4,750 $ (557 ) $ 5,853 (a) Restricted cash balances relate primarily to Ally securitization arrangements. Refer to Note 11 for additional details describing the nature of restricted cash balances.

Contingencies and Other Risks

Contingencies and Other Risks	6 Months Ended
	Jun. 30, 2018
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 business lines 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). In November 2017, the plaintiffs filed a consolidated amended complaint. In April 2018, the court entered a scheduling order setting deadlines for briefing of defendants’ joint motion for summary disposition. 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 responded timely to each of the requests. 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 in our 2017 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	6 Months Ended
	Jun. 30, 2018
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events Declaration of Quarterly Dividend On July 13, 2018 , the Board declared a quarterly cash dividend of $0.15 per share on all common stock. The dividend is payable on August 15, 2018 , to stockholders of record at the close of business on August 1, 2018.

Description of Business, Basi32

Description of Business, Basis of Presentation, and Changes in Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2018
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. 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.
Investment, Policy [Policy Text Block]	Our investment portfolio includes various debt and equity securities. Our debt securities include government securities, corporate bonds, asset-backed securities (ABS), and mortgage-backed securities (MBS). Debt securities are classified based on management’s intent to sell or hold the security. We classify debt securities as held-to-maturity only when we have both the intent and ability to hold the securities to maturity. We classify debt securities as trading when the securities are acquired for the purpose of selling or holding them for a short period of time. Debt securities not classified as either held-to-maturity or trading are classified as available-for-sale. Our portfolio includes debt securities classified as available-for-sale and held-to-maturity. Our available-for-sale debt securities are carried at fair value with unrealized gains and losses included in accumulated other comprehensive loss and are subject to impairment. Our held-to-maturity debt securities are carried at amortized cost and are subject to impairment. We assess our available-for-sale and held-to-maturity debt securities for potential other-than-temporary impairment. We employ a methodology that considers available evidence in evaluating potential other-than-temporary impairment of our debt securities. If the cost of an investment exceeds its fair value, we evaluate, among other factors, the magnitude and duration of the decline in fair value. We also evaluate the financial health of and business outlook for the issuer, the performance of the underlying assets for interests in securitized assets, and, for debt securities classified as available-for-sale, our intent and ability to hold the investment through recovery of its amortized cost basis. Once a decline in fair value of a debt security is determined to be other-than-temporary, an impairment charge for the credit component is recorded to other gain (loss) on investments, net, in our Condensed Consolidated Statement of Comprehensive Income, and a new cost basis in the investment is established. The noncredit loss component of an available-for-sale debt security continues to be recorded in other comprehensive (loss) income when we do not intend to sell the security and it is not more likely than not that we will have to sell the security prior to the security’s anticipated recovery. Both the credit and noncredit loss components are recorded in earnings when we intend to sell the security or it is more likely than not that we will have to sell the security prior to the security’s anticipated recovery. Subsequent increases and decreases to the fair value of available-for-sale debt securities are included in other comprehensive (loss) income, so long as they are not attributable to another other-than-temporary impairment. We amortize premiums and discounts on debt securities as an adjustment to investment yield generally over the stated maturity of the security. For ABS and MBS where prepayments can be reasonably estimated, amortization is adjusted for expected prepayments. Our investment in equity securities includes securities that are recognized at fair value with changes in the fair value recorded in earnings, and equity securities that are recognized using other measurement principles. Effective January 1, 2018, equity securities that have a readily determinable fair value, as well as certain investments that do not have a readily determinable fair value and are not eligible to be recognized using other measurement principles, are recorded at fair value with changes in fair value recorded in earnings and reported in other gain (loss) on investments, net in our Condensed Consolidated Statement of Comprehensive Income . These investments, which are primarily attributable to the investment portfolio of our Insurance operations, are included in equity securities on our Condensed Consolidated Balance Sheet . Refer to Note 6 for further information on our equity securities that have a readily determinable market value. Our equity securities recognized using other measurement principles include investments in Federal Home Loan Bank (FHLB) and Federal Reserve Bank (FRB) stock held to meet regulatory requirements, equity investments related to low income housing tax credits and the Community Reinvestment Act (CRA), which do not have a readily determinable fair value, and other equity investments that do not have a readily determinable fair value. Our low income housing tax credit investments are accounted for using the proportional amortization method of accounting for qualified affordable housing investments. Our obligations related to unfunded commitments for our low income housing tax credit investments are included in other liabilities. The majority of our CRA investments are accounted for using the equity method of accounting. Our investments in low income housing tax credits and CRA investments are included in other assets on our Condensed Consolidated Balance Sheet. Our investments in FHLB and FRB stock are carried at cost. Our remaining investments in equity securities are recorded at cost, less impairment and adjusted for observable price changes under the measurement alternative provided under GAAP. These investments, along with our investments in FHLB and FRB stock, are included in nonmarketable equity investments in other assets on our Condensed Consolidated Balance Sheet. As conditions warrant, we review these investments for impairment and adjust the carrying value of the investment if it is deemed to be impaired. Investments recorded under the measurement alternative are also reviewed at each reporting period to determine if any adjustments are required for observable price changes in identical or similar securities of the same issuer. Realized gains and losses on the sale of securities are determined using the specific identification method and are reported in other gain (loss) on investments, net in our Condensed Consolidated Statement of Comprehensive Income.
Derivatives, Policy [Policy Text Block]	We use derivative instruments primarily for risk management purposes. We do not use derivative instruments for speculative purposes. Certain of our derivative instruments are designated as accounting hedges in qualifying relationships, whereas other derivative instruments have not been designated as accounting hedges. In accordance with applicable accounting standards, all derivative instruments, whether designated for hedge accounting or not, are required to be recorded on the balance sheet as assets or liabilities and measured at fair value. We have elected to report the fair value of derivative assets and liabilities on a gross basis—including the fair value for the right to reclaim cash collateral or the obligation to return cash collateral—arising from instruments executed with the same counterparty under a master netting arrangement where we do not have the intent to offset. For additional information on derivative instruments and hedging activities, refer to Note 18 . At the inception of a hedge accounting relationship, we designate each qualifying hedge relationship as a hedge of the fair value of a specifically identified asset or liability (fair value hedge); as a hedge of the variability of cash flows to be received or paid, or forecasted to be received or paid, related to a recognized asset or liability (cash flow hedge); or as a hedge of the foreign-currency exposure of a net investment in a foreign operation (net investment hedge). We formally document all relationships between hedging instruments and hedged items, as well as the risk management objectives for undertaking various hedge transactions. Both at hedge inception and on an ongoing basis, we formally assess whether the derivatives that are used in hedging relationships are highly effective in offsetting changes in the fair values or cash flows of hedged items. Changes in the fair value of derivative instruments qualifying as fair value hedges, along with the gain or loss on the hedged asset or liability attributable to the hedged risk, are recorded in current period earnings. For qualifying cash flow hedges, the changes in fair value of the derivative financial instruments are recorded in accumulated other comprehensive loss and recognized in the income statement when the hedged cash flows affect earnings. For a qualifying net investment hedge, the gain or loss is reported in accumulated other comprehensive loss as part of the cumulative translation adjustment. Hedge accounting treatment is no longer applied if a derivative financial instrument is terminated, or if the hedge designation is removed or assessed to be no longer highly effective. For terminated fair value hedges, any changes to the hedged asset or liability remain as part of the basis of the hedged asset or liability and are recognized into income over the remaining life of the asset or liability. For terminated cash flow hedges, unless it is probable that the forecasted cash flows will not occur within a specified period, any changes in fair value of the derivative financial instrument previously recognized remain in accumulated other comprehensive loss, and are reclassified into earnings in the same period that the hedged cash flows affect earnings. Any previously recognized gain or loss for a net investment hedge continues to remain in accumulated other comprehensive loss until earnings are impacted by sale or liquidation of the associated foreign operation. In all instances, after hedge accounting is no longer applied, any subsequent changes in fair value of the derivative instrument will be recorded into earnings. Changes in the fair value of derivative financial instruments held for risk management purposes that are not designated as accounting hedges under GAAP are reported in current period earnings.
Income Tax, Policy [Policy Text Block]	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 2017 Annual Report on Form 10-K, which describes our annual significant income tax accounting policy and related methodology.
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Standards Statement of Cash Flows — Restricted Cash (ASU 2016-18) As of December 31, 2017, we elected to early-adopt Accounting Standards Update (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. The amendments were applied retrospectively to all periods presented within the statement of cash flows. The implementation of this guidance resulted in a change in presentation of our Condensed Consolidated Statement of Cash Flows and additional disclosures surrounding restricted cash balances, but did not result in a change to our Condensed Consolidated Statement of Comprehensive Income or Condensed Consolidated Balance Sheet. Revenue from Contracts with Customers (ASU 2014-09) 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. 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. The FASB issued several additional ASUs to clarify guidance and provide implementation support for ASU 2014-09. The clarifying guidance elaborates on the key concepts within ASU 2014-09 and clarifies how those concepts interact with other GAAP requirements. On January 1, 2018, we adopted ASU 2014-09 and all subsequent ASUs that modified ASU 2014-09 (collectively, the amendments to the revenue recognition principles), which have been codified in ASC 606, Revenue from Contracts with Customers, and ASC 610-20, Gains and Losses from the Derecognition of Nonfinancial Assets , respectively. We elected to adopt this guidance using the modified retrospective approach applied to all contracts with customers that were not completed as of January 1, 2018. The adoption of the amendments resulted in a reduction to our opening retained earnings of approximately $126 million , net of income taxes. Refer to Note 2 for further details. Financial Instruments — Recognition and Measurement of Financial Assets (ASU 2016-01) As of January 1, 2018, we adopted 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. The FASB subsequently issued ASU 2018-03 to clarify guidance and provide implementation support for ASU 2016-01, which we elected to early-adopt as of January 1, 2018, to align with the adoption of ASU 2016-01. 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 are no longer recognized through other comprehensive (loss) income , which creates additional volatility in our Condensed Consolidated Statement of Comprehensive Income. Reporting entities may continue to elect to measure certain 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 (loss) income and not as a component of net income. We adopted these amendments, as required, on a modified retrospective basis with a cumulative effect adjustment as of the beginning of the fiscal year of initial adoption. The adoption of the amendments resulted in a reduction to our opening retained earnings of approximately $20 million , net of income taxes. Derivatives and Hedging — Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12) As of January 1, 2018, we elected to early-adopt ASU 2017-12. The amendments in this update enhance the financial reporting of hedging relationships to better align hedge accounting with an entity’s risk management activities. This update also makes certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP and better portrays economic results through changes to both the designation and measurement guidance for qualifying hedging relationships and presentation of hedge results. We adopted the amendments to all cash flow and net investment hedge relationships that existed on the date of adoption using a modified retrospective approach. No cumulative effect adjustment to our opening retained earnings was required as a result of the adoption. The presentation and disclosure requirements included in this update were adopted prospectively. Refer to Note 18 for further details. Accumulated Other Comprehensive Income — Reclassification of Certain Tax Effects (ASU 2018-02) In February 2018, the FASB issued ASU 2018-02. The amendments in this update provide guidance concerning the treatment of the impact of income tax effects resulting from the Tax Cuts and Jobs Act of 2017 (the Tax Act) on items included in accumulated other comprehensive income. Our policy is to use the portfolio method with respect to reclassification of stranded income tax effects in accumulated other comprehensive loss. The amendments in ASU 2018-02 provide entities an election to reclassify the income tax effect of the Tax Act from accumulated other comprehensive income to retained earnings. We elected to early-adopt this standard as of January 1, 2018, and reclassified the effect of the change in the federal corporate income tax rate on items included in accumulated other comprehensive loss. This election resulted in a reclassification of $42 million from accumulated other comprehensive loss to retained earnings. Recently Issued Accounting Standards 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. We are currently in the process of reviewing our lease contracts and examining the practical expedients and accounting policy elections provided in the amendments, as well as ensuring our control environment and reporting processes reflect the requirements of the amendments. Upon adoption, our balance sheet will include a right-of-use asset and lease liability for our operating leases where we are the lessee, which primarily include our facilities leases. In addition, we will no longer capitalize certain initial direct costs in connection with lease originations where we are the lessor. We do not anticipate the adoption of these amendments will have a material impact to our financial statements. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as currently 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 recorded under the current incurred loss model 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. The amount of the change in the allowance for credit losses will also be impacted by the composition of our portfolio at the adoption date, as well as economic conditions and forecasts at that time. Management created a cross-functional working group to govern the implementation of these amendments, including consideration of model development, data integrity, technology, reporting and disclosure requirements, key accounting interpretations, control environment, and corporate governance. 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. 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. While our assessment is not final, we do not expect the amendments to have a material impact to our financial statements and are currently in the process of ensuring our control environment and reporting processes reflect the requirements of the amendments. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as required.
Accounting Standards Update 2016-18 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	As of December 31, 2017, we elected to early-adopt Accounting Standards Update (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. The amendments were applied retrospectively to all periods presented within the statement of cash flows. The implementation of this guidance resulted in a change in presentation of our Condensed Consolidated Statement of Cash Flows and additional disclosures surrounding restricted cash balances, but did not result in a change to our Condensed Consolidated Statement of Comprehensive Income or Condensed Consolidated Balance Sheet.
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	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. 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. The FASB issued several additional ASUs to clarify guidance and provide implementation support for ASU 2014-09. The clarifying guidance elaborates on the key concepts within ASU 2014-09 and clarifies how those concepts interact with other GAAP requirements. On January 1, 2018, we adopted ASU 2014-09 and all subsequent ASUs that modified ASU 2014-09 (collectively, the amendments to the revenue recognition principles), which have been codified in ASC 606, Revenue from Contracts with Customers, and ASC 610-20, Gains and Losses from the Derecognition of Nonfinancial Assets , respectively. We elected to adopt this guidance using the modified retrospective approach applied to all contracts with customers that were not completed as of January 1, 2018. The adoption of the amendments resulted in a reduction to our opening retained earnings of approximately $126 million , net of income taxes. Refer to Note 2 for further details.
Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	As of January 1, 2018, we adopted 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. The FASB subsequently issued ASU 2018-03 to clarify guidance and provide implementation support for ASU 2016-01, which we elected to early-adopt as of January 1, 2018, to align with the adoption of ASU 2016-01. 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 are no longer recognized through other comprehensive (loss) income , which creates additional volatility in our Condensed Consolidated Statement of Comprehensive Income. Reporting entities may continue to elect to measure certain 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 (loss) income and not as a component of net income. We adopted these amendments, as required, on a modified retrospective basis with a cumulative effect adjustment as of the beginning of the fiscal year of initial adoption. The adoption of the amendments resulted in a reduction to our opening retained earnings of approximately $20 million , net of income taxes
Accounting Standards Update 2017-12 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	As of January 1, 2018, we elected to early-adopt ASU 2017-12. The amendments in this update enhance the financial reporting of hedging relationships to better align hedge accounting with an entity’s risk management activities. This update also makes certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP and better portrays economic results through changes to both the designation and measurement guidance for qualifying hedging relationships and presentation of hedge results. We adopted the amendments to all cash flow and net investment hedge relationships that existed on the date of adoption using a modified retrospective approach. No cumulative effect adjustment to our opening retained earnings was required as a result of the adoption. The presentation and disclosure requirements included in this update were adopted prospectively. Refer to Note 18 for further details.
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	In February 2018, the FASB issued ASU 2018-02. The amendments in this update provide guidance concerning the treatment of the impact of income tax effects resulting from the Tax Cuts and Jobs Act of 2017 (the Tax Act) on items included in accumulated other comprehensive income. Our policy is to use the portfolio method with respect to reclassification of stranded income tax effects in accumulated other comprehensive loss. The amendments in ASU 2018-02 provide entities an election to reclassify the income tax effect of the Tax Act from accumulated other comprehensive income to retained earnings. We elected to early-adopt this standard as of January 1, 2018, and reclassified the effect of the change in the federal corporate income tax rate on items included in accumulated other comprehensive loss. This election resulted in a reclassification of $42 million from accumulated other comprehensive loss to retained earnings.
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	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. We are currently in the process of reviewing our lease contracts and examining the practical expedients and accounting policy elections provided in the amendments, as well as ensuring our control environment and reporting processes reflect the requirements of the amendments. Upon adoption, our balance sheet will include a right-of-use asset and lease liability for our operating leases where we are the lessee, which primarily include our facilities leases. In addition, we will no longer capitalize certain initial direct costs in connection with lease originations where we are the lessor. We do not anticipate the adoption of these amendments will have a material impact to our financial statements. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as currently required.
Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	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 recorded under the current incurred loss model 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. The amount of the change in the allowance for credit losses will also be impacted by the composition of our portfolio at the adoption date, as well as economic conditions and forecasts at that time. Management created a cross-functional working group to govern the implementation of these amendments, including consideration of model development, data integrity, technology, reporting and disclosure requirements, key accounting interpretations, control environment, and corporate governance. 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.
Accounting Standards Update 2017-08 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	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. While our assessment is not final, we do not expect the amendments to have a material impact to our financial statements and are currently in the process of ensuring our control environment and reporting processes reflect the requirements of the amendments. We currently plan to adopt these amendments on January 1, 2019, and expect to use the modified retrospective approach as required.

Fair Value Fair Value (Policies

Fair Value Fair Value (Policies)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurement, Policy [Policy Text Block]	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.

Revenue from Contracts with C34

Revenue from Contracts with Customers (Tables)	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The following table presents the impact to our Condensed Consolidated Balance Sheet as of January 1, 2018, as a result of adopting the amendments to the revenue recognition principles. ($ in millions) As reported, December 31, 2017 Adjustment related to adoption As adjusted, January 1, 2018 Assets Premiums receivable and other insurance assets $ 2,047 $ 122 $ 2,169 Other assets 5,663 41 5,704 Total assets $ 167,148 $ 163 $ 167,311 Liabilities Unearned insurance premiums and service revenue $ 2,604 $ 289 $ 2,893 Total liabilities 153,654 289 153,943 Equity Accumulated deficit (6,406 ) (126 ) (6,532 ) Total equity 13,494 (126 ) 13,368 Total liabilities and equity $ 167,148 $ 163 $ 167,311
Impact of ASU 2014-09 on Balance Sheet and Income Statement [Table Text Block]	The following tables present the impact of adopting the amendments to the revenue recognition principles to our Condensed Consolidated Statement of Comprehensive Income and Condensed Consolidated Balance Sheet . Three months ended June 30, 2018 Six months ended June 30, 2018 ($ in millions) As reported Effect of adoption As reported Effect of adoption Other revenue Insurance premiums and service revenue earned $ 239 $ (9 ) $ 495 $ (15 ) Total other revenue 364 (9 ) 718 (15 ) Total net revenue 1,458 (9 ) 2,861 (15 ) Noninterest expense Compensation and benefits expense 292 (1 ) 598 (2 ) Other operating expenses 446 (3 ) 891 (5 ) Total noninterest expense 839 (4 ) 1,653 (7 ) Income from continuing operations before income tax expense 461 (5 ) 789 (8 ) Income tax expense from continuing operations 113 (1 ) 189 (2 ) Net income from continuing operations 348 (4 ) 600 (6 ) Net income 349 (4 ) 599 (6 ) Comprehensive income $ 279 $ (4 ) $ 201 $ (6 ) June 30, 2018 ($ in millions) As reported Effect of adoption Assets Premiums receivable and other insurance assets $ 2,247 $ 128 Other assets 6,014 43 Total assets 171,345 171 Liabilities Unearned insurance premiums and service revenue $ 2,957 $ 304 Total liabilities 158,206 304 Equity Accumulated deficit (6,026 ) (133 ) Total equity 13,139 (133 ) Total liabilities and equity $ 171,345 $ 171
Disaggregation of Revenue [Table Text Block]	The following table presents a disaggregated view of our revenue from contracts with customers included in other revenue that falls within the scope of the amendments to the revenue recognition principles. Three months ended June 30, 2018 ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated Revenue from contracts with customers Noninsurance contracts $ — $ 125 $ — $ — $ — $ 125 Remarketing fee income 21 — — — — 21 Brokerage commissions and other revenue — — — — 15 15 Brokered/agent commissions — 4 — — — 4 Deposit account and other banking fees — — — — 3 3 Other 4 — — — — 4 Total revenue from contracts with customers 25 129 — — 18 172 All other revenue 38 137 2 14 1 192 Total other revenue (a) $ 63 $ 266 $ 2 $ 14 $ 19 $ 364 (a) Represents a component of total net revenue. Refer to Note 22 for further information on our reportable operating segments. Six months ended June 30, 2018 ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated Revenue from contracts with customers Noninsurance contracts $ — $ 248 $ — $ — $ — $ 248 Remarketing fee income 44 — — — — 44 Brokerage commissions and other revenue — — — — 31 31 Brokered/agent commissions — 8 — — — 8 Deposit account and other banking fees — — — — 6 6 Other 6 1 — — — 7 Total revenue from contracts with customers 50 257 — — 37 344 All other revenue 79 255 3 22 15 374 Total other revenue (a) $ 129 $ 512 $ 3 $ 22 $ 52 $ 718 (a) Represents a component of total net revenue. Refer to Note 22 for further information on our reportable operating segments. In addition to the components of other revenue presented above, as part of our Automotive Finance operations, we recognized gains of $16 million and $34 million for the three months and six months ended June 30, 2018 , respectively, on the sale of off-lease vehicles. These gains are included in depreciation expense on operating lease assets in our Condensed Consolidated Statement of Comprehensive Income .

Other Income, Net of Losses (Ta

Other Income, Net of Losses (Tables)	6 Months Ended
	Jun. 30, 2018
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 June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Late charges and other administrative fees $ 25 $ 25 $ 54 $ 52 Remarketing fees 21 27 44 56 Servicing fees 8 14 16 30 Income from equity-method investments 7 5 13 5 Other, net 36 31 79 73 Total other income, net of losses $ 97 $ 102 $ 206 $ 216

Reserves for Insurance Losses36

Reserves for Insurance Losses and Loss Adjustment Expenses (Tables)	6 Months Ended
	Jun. 30, 2018
Reserves for Insurance Losses and Loss Adjustment Expense [Abstract]
Short-Duration Insurance and Deposit Contracts [Text Block]	The following table shows a rollforward of our reserves for insurance losses and loss adjustment expenses. ($ in millions) 2018 2017 Total gross reserves for insurance losses and loss adjustment expenses at January 1, $ 140 $ 149 Less: Reinsurance recoverable 108 108 Net reserves for insurance losses and loss adjustment expenses at January 1, 32 41 Net insurance losses and loss adjustment expenses incurred related to: Current year 159 211 Prior years (a) 5 2 Total net insurance losses and loss adjustment expenses incurred 164 213 Net insurance losses and loss adjustment expenses paid or payable related to: Current year (121 ) (183 ) Prior years (26 ) (27 ) Total net insurance losses and loss adjustment expenses paid or payable (147 ) (210 ) Net reserves for insurance losses and loss adjustment expenses at June 30, 49 44 Plus: Reinsurance recoverable 100 135 Total gross reserves for insurance losses and loss adjustment expenses at June 30, $ 149 $ 179 (a) There have been no material adverse changes to the reserve for prior years.

Other Operating Expenses (Table

Other Operating Expenses (Tables)	6 Months Ended
	Jun. 30, 2018
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 June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Insurance commissions $ 109 $ 104 $ 219 $ 203 Technology and communications 74 71 145 140 Lease and loan administration 40 39 82 75 Advertising and marketing 29 33 68 63 Professional services 35 27 67 53 Regulatory and licensing fees 35 28 65 55 Vehicle remarketing and repossession 26 25 58 53 Premises and equipment depreciation 22 23 42 45 Occupancy 11 11 22 23 Non-income taxes 6 8 14 16 Amortization of intangible assets 3 3 6 6 Other 56 48 103 93 Total other operating expenses $ 446 $ 420 $ 891 $ 825

Investment Securities (Tables)

Investment Securities (Tables)	6 Months Ended
	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Marketable Securities [Table Text Block]	Our portfolio of available-for-sale and held-to-maturity debt securities includes bonds, asset-backed securities, commercial and residential mortgage-backed securities, and other investments. We also hold equity securities. The cost, fair value, and gross unrealized gains and losses on available-for-sale and held-to-maturity investment securities were as follows. June 30, 2018 December 31, 2017 Amortized cost Gross unrealized Fair value Amortized cost Gross unrealized Fair value ($ in millions) gains losses gains losses Available-for-sale securities Debt securities U.S. Treasury $ 1,963 $ 1 $ (90 ) $ 1,874 $ 1,831 $ — $ (54 ) $ 1,777 U.S. States and political subdivisions 865 5 (19 ) 851 850 11 (7 ) 854 Foreign government 155 1 (2 ) 154 153 2 (1 ) 154 Agency mortgage-backed residential 15,559 4 (497 ) 15,066 14,412 35 (156 ) 14,291 Mortgage-backed residential 2,716 2 (93 ) 2,625 2,517 11 (34 ) 2,494 Mortgage-backed commercial 644 1 (3 ) 642 541 1 (1 ) 541 Asset-backed 870 2 (4 ) 868 933 4 (1 ) 936 Corporate debt 1,258 1 (43 ) 1,216 1,262 5 (11 ) 1,256 Total available-for-sale securities (a) (b) (c) $ 24,030 $ 17 $ (751 ) $ 23,296 $ 22,499 $ 69 $ (265 ) $ 22,303 Held-to-maturity securities Debt securities Agency mortgage-backed residential (d) $ 2,062 $ 1 $ (83 ) $ 1,980 $ 1,863 $ 3 $ (37 ) $ 1,829 Asset-backed retained notes 27 — — 27 36 — — 36 Total held-to-maturity securities $ 2,089 $ 1 $ (83 ) $ 2,007 $ 1,899 $ 3 $ (37 ) $ 1,865 (a) Certain entities related to our Insurance operations are required to deposit securities with state regulatory authorities. These deposited securities totaled $12 million at both June 30, 2018 , and December 31, 2017. (b) Certain available-for-sale securities are included in fair value hedging relationships. Refer to Note 18 for additional information. (c) Investment securities with a fair value of $7.1 billion and $7.8 billion at June 30, 2018 , and December 31, 2017 , respectively, were pledged to secure advances from the 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 $1.2 billion and $1.0 billion of the underlying investment securities at June 30, 2018 , and December 31, 2017 , respectively. (d) Securities with a fair value of $962 million and $664 million at June 30, 2018 , and December 31, 2017, respectively, were pledged to secure advances from the FHLB.
Investments Classified by Contractual Maturity Date [Table Text Block]	The maturity distribution of debt securities outstanding is summarized in the following tables. Call or prepayment options may cause actual maturities to differ from contractual maturities. Total Due in one year or less Due after one year through five years Due after five years through ten years Due after ten years ($ in millions) Amount Yield Amount Yield Amount Yield Amount Yield Amount Yield June 30, 2018 Fair value of available-for-sale securities (a) U.S. Treasury $ 1,874 1.9 % $ 13 1.4 % $ 578 1.9 % $ 1,283 1.8 % $ — — % U.S. States and political subdivisions 851 3.1 35 3.4 53 2.2 237 2.6 526 3.4 Foreign government 154 2.5 25 3.3 61 2.3 68 2.4 — — Agency mortgage-backed residential 15,066 3.2 — — — — 25 2.0 15,041 3.2 Mortgage-backed residential 2,625 3.2 — — — — — — 2,625 3.2 Mortgage-backed commercial 642 3.6 — — — — 31 3.6 611 3.6 Asset-backed 868 3.3 — — 618 3.3 137 3.6 113 3.0 Corporate debt 1,216 3.1 122 2.8 472 2.7 589 3.3 33 4.9 Total available-for-sale securities $ 23,296 3.1 $ 195 2.9 $ 1,782 2.6 $ 2,370 2.4 $ 18,949 3.2 Amortized cost of available-for-sale securities $ 24,030 $ 195 $ 1,811 $ 2,476 $ 19,548 Amortized cost of held-to-maturity securities Agency mortgage-backed residential $ 2,062 3.1 % $ — — % $ — — % $ — — % $ 2,062 3.1 % Asset-backed retained notes 27 1.8 — — 26 1.8 1 3.0 — — Total held-to-maturity securities $ 2,089 3.1 $ — — $ 26 1.8 $ 1 3.0 $ 2,062 3.1 December 31, 2017 Fair value of available-for-sale securities (a) U.S. Treasury $ 1,777 1.7 % $ — — % $ 487 1.7 % $ 1,290 1.8 % $ — — % U.S. States and political subdivisions 854 2.9 76 1.8 36 2.3 203 2.5 539 3.3 Foreign government 154 2.5 — — 80 2.5 74 2.4 — — Agency mortgage-backed residential 14,291 3.1 — — — — 3 2.9 14,288 3.1 Mortgage-backed residential 2,494 3.1 — — — — — — 2,494 3.1 Mortgage-backed commercial 541 3.2 — — 30 3.1 31 3.1 480 3.2 Asset-backed 936 3.1 — — 698 3.1 106 3.1 132 2.8 Corporate debt 1,256 2.9 140 2.6 513 2.6 564 3.2 39 4.7 Total available-for-sale securities $ 22,303 3.0 $ 216 2.3 $ 1,844 2.5 $ 2,271 2.3 $ 17,972 3.1 Amortized cost of available-for-sale securities $ 22,499 $ 217 $ 1,852 $ 2,314 $ 18,116 Amortized cost of held-to-maturity securities Agency mortgage-backed residential $ 1,863 3.1 % $ — — % $ — — % $ — — % $ 1,863 3.1 % Asset-backed retained notes 36 1.7 — — 35 1.7 1 3.0 — — Total held-to-maturity securities $ 1,899 3.1 $ — — $ 35 1.7 $ 1 3.0 $ 1,863 3.1 (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.
Investment Income [Table Text Block]	The following table presents interest and dividends on investment securities. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Taxable interest $ 164 $ 130 $ 318 $ 249 Taxable dividends 3 3 6 5 Interest and dividends exempt from U.S. federal income tax 6 6 12 11 Interest and dividends on investment securities $ 173 $ 139 $ 336 $ 265
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, and net gains or losses on equity securities held during the period. There were no other-than-temporary impairments of available-for-sale securities for either period. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Available-for-sale securities Gross realized gains $ 1 $ 24 $ 7 $ 51 Gross realized losses (a) — (1 ) — (1 ) Net realized gains on available-for-sale securities 1 23 7 50 Net realized gain on equity securities 18 40 Net unrealized gain (loss) on equity securities (b) 8 (32 ) Other gain on investments, net $ 27 $ 23 $ 15 $ 50 (a) Certain available-for-sale securities were sold at a loss in 2018 and 2017 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. (b) As a result of our adoption of ASU 2016-01, beginning January 1, 2018, changes in the fair value of our portfolio of equity securities are recognized in net income. Prior to adoption, equity securities were included in our available-for-sale portfolio and unrealized changes in fair value were recognized through other comprehensive (loss) income until realized, at which point we recorded a gain or loss on sale. We adopted ASU 2016-01 on January 1, 2018, on a modified retrospective basis with a cumulative effect adjustment as of the beginning of the fiscal year of initial adoption. Refer to the section titled Recently Adopted Accounting Standards in Note 1 for additional information.
Schedule of Unrealized Loss on Investments [Table Text Block]	The table below summarizes available-for-sale and held-to-maturity securities in an unrealized loss position, which we evaluated for other than temporary impairment applying the methodology described in Note 1 . As of June 30, 2018 , we did not have the intent to sell the available-for-sale or held-to-maturity securities with an unrealized loss position and we do not believe it is more likely than not that we will be required to sell these securities before recovery of their amortized cost basis. As a result of this evaluation, we believe that the securities with an unrealized loss position are not considered to be other-than-temporarily impaired at June 30, 2018 . June 30, 2018 December 31, 2017 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 $ 485 $ (19 ) $ 1,275 $ (71 ) $ 471 $ (8 ) $ 1,305 $ (46 ) U.S. States and political subdivisions 420 (8 ) 181 (11 ) 242 (2 ) 183 (5 ) Foreign government 56 (1 ) 25 (1 ) 80 (1 ) 4 — Agency mortgage-backed residential 8,834 (215 ) 5,331 (282 ) 4,066 (19 ) 5,671 (137 ) Mortgage-backed residential 1,642 (35 ) 688 (58 ) 857 (2 ) 773 (32 ) Mortgage-backed commercial 91 (2 ) 18 (1 ) 76 (1 ) 21 — Asset-backed 479 (3 ) 71 (1 ) 220 (1 ) 91 — Corporate debt 885 (26 ) 254 (17 ) 529 (4 ) 194 (7 ) Total temporarily impaired available-for-sale securities $ 12,892 $ (309 ) $ 7,843 $ (442 ) $ 6,541 $ (38 ) $ 8,242 $ (227 ) Held-to-maturity securities Agency mortgage-backed residential $ 1,152 $ (33 ) $ 668 $ (50 ) $ 773 $ (5 ) $ 687 $ (32 ) Asset-backed retained certificates 24 — — — 35 — — — Total held-to-maturity debt securities $ 1,176 $ (33 ) $ 668 $ (50 ) $ 808 $ (5 ) $ 687 $ (32 )

Finance Receivables and Loans39

Finance Receivables and Loans, Net (Tables)	6 Months Ended
	Jun. 30, 2018
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) June 30, 2018 December 31, 2017 Consumer automotive (a) $ 70,473 $ 68,071 Consumer mortgage Mortgage Finance (b) 13,328 11,657 Mortgage — Legacy (c) 1,803 2,093 Total consumer mortgage 15,131 13,750 Total consumer 85,604 81,821 Commercial Commercial and industrial Automotive 31,501 33,025 Other 4,027 3,887 Commercial real estate 4,412 4,160 Total commercial 39,940 41,072 Total finance receivables and loans (d) $ 125,544 $ 122,893 (a) Certain finance receivables and loans are included in fair value hedging relationships. Refer to Note 18 for additional information. (b) Includes loans originated as interest-only mortgage loans of $18 million and $20 million at June 30, 2018 , and December 31, 2017 , respectively, 36% of which are expected to start principal amortization in 2019 , and 48% in 2020 . The remainder of these loans have exited the interest-only period. (c) Includes loans originated as interest-only mortgage loans of $416 million and $496 million at June 30, 2018 , and December 31, 2017 , respectively, of which 99% have exited the interest-only period. (d) Totals include net unearned income, unamortized premiums and discounts, and deferred fees and costs of $612 million and $551 million at June 30, 2018 , and December 31, 2017 , respectively
Allowance for Credit Losses on Financing Receivables [Table Text Block]	The following tables present an analysis of the activity in the allowance for loan losses on finance receivables and loans. Three months ended June 30, 2018 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at April 1, 2018 $ 1,066 $ 74 $ 138 $ 1,278 Charge-offs (a) (296 ) (8 ) (2 ) (306 ) Recoveries 114 6 6 126 Net charge-offs (182 ) (2 ) 4 (180 ) Provision for loan losses 168 (4 ) (6 ) 158 Other 1 (2 ) 2 1 Allowance at June 30, 2018 $ 1,053 $ 66 $ 138 $ 1,257 (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 2017 Annual Report on Form 10-K for more information regarding our charge-off policies. Three months ended June 30, 2017 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at April 1, 2017 $ 941 $ 86 $ 128 $ 1,155 Charge-offs (a) (290 ) (6 ) — (296 ) Recoveries 91 6 — 97 Net charge-offs (199 ) — — (199 ) Provision for loan losses 260 (3 ) 12 269 Allowance at June 30, 2017 $ 1,002 $ 83 $ 140 $ 1,225 (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 2017 Annual Report on Form 10-K for more information regarding our charge-off policies. Six months ended June 30, 2018 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at January 1, 2018 $ 1,066 $ 79 $ 131 $ 1,276 Charge-offs (a) (661 ) (20 ) (2 ) (683 ) Recoveries 226 12 6 244 Net charge-offs (435 ) (8 ) 4 (439 ) Provision for loan losses 421 (3 ) 1 419 Other 1 (2 ) 2 1 Allowance at June 30, 2018 $ 1,053 $ 66 $ 138 $ 1,257 Allowance for loan losses at June 30, 2018 Individually evaluated for impairment $ 42 $ 24 $ 27 $ 93 Collectively evaluated for impairment 1,011 42 111 1,164 Finance receivables and loans at gross carrying value Ending balance $ 70,473 $ 15,131 $ 39,940 $ 125,544 Individually evaluated for impairment 480 228 198 906 Collectively evaluated for impairment 69,993 14,903 39,742 124,638 (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 2017 Annual Report on Form 10-K for more information regarding our charge-off policies. Six months ended June 30, 2017 ($ in millions) Consumer automotive Consumer mortgage Commercial Total Allowance at January 1, 2017 $ 932 $ 91 $ 121 $ 1,144 Charge-offs (a) (631 ) (15 ) — (646 ) Recoveries 181 13 — 194 Net charge-offs (450 ) (2 ) — (452 ) Provision for loan losses 527 (6 ) 19 540 Other (b) (7 ) — — (7 ) Allowance at June 30, 2017 $ 1,002 $ 83 $ 140 $ 1,225 Allowance for loan losses at June 30, 2017 Individually evaluated for impairment $ 34 $ 31 $ 32 $ 97 Collectively evaluated for impairment 968 52 108 1,128 Finance receivables and loans at gross carrying value Ending balance $ 66,774 $ 11,294 $ 42,460 $ 120,528 Individually evaluated for impairment 380 242 151 773 Collectively evaluated for impairment 66,394 11,052 42,309 119,755 (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 2017 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 based on net carrying value. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Consumer automotive $ — $ 85 $ — $ 1,298 Consumer mortgage 4 3 5 6 Total sales and transfers $ 4 $ 88 $ 5 $ 1,304
Schedule of Purchases of Financing Receivables and Loans [Table Text Block]	The following table presents information about significant purchases of finance receivables and loans based on unpaid principal balance at the time of purchase. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Consumer automotive $ 233 $ 611 $ 401 $ 679 Consumer mortgage 852 809 2,147 1,136 Total purchases of finance receivables and loans $ 1,085 $ 1,420 $ 2,548 $ 1,815
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 June 30, 2018 Consumer automotive $ 1,706 $ 387 $ 248 $ 2,341 $ 68,132 $ 70,473 Consumer mortgage Mortgage Finance 50 4 11 65 13,263 13,328 Mortgage — Legacy 38 14 54 106 1,697 1,803 Total consumer mortgage 88 18 65 171 14,960 15,131 Total consumer 1,794 405 313 2,512 83,092 85,604 Commercial Commercial and industrial Automotive — — 21 21 31,480 31,501 Other 4 — — 4 4,023 4,027 Commercial real estate — — — — 4,412 4,412 Total commercial 4 — 21 25 39,915 39,940 Total consumer and commercial $ 1,798 $ 405 $ 334 $ 2,537 $ 123,007 $ 125,544 December 31, 2017 Consumer automotive $ 1,994 $ 478 $ 268 $ 2,740 $ 65,331 $ 68,071 Consumer mortgage Mortgage Finance 60 11 18 89 11,568 11,657 Mortgage — Legacy 43 25 62 130 1,963 2,093 Total consumer mortgage 103 36 80 219 13,531 13,750 Total consumer 2,097 514 348 2,959 78,862 81,821 Commercial Commercial and industrial Automotive 5 — 3 8 33,017 33,025 Other — — — — 3,887 3,887 Commercial real estate — — — — 4,160 4,160 Total commercial 5 — 3 8 41,064 41,072 Total consumer and commercial $ 2,102 $ 514 $ 351 $ 2,967 $ 119,926 $ 122,893
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) June 30, 2018 December 31, 2017 Consumer automotive $ 602 $ 603 Consumer mortgage Mortgage Finance 18 25 Mortgage — Legacy 87 92 Total consumer mortgage 105 117 Total consumer 707 720 Commercial Commercial and industrial Automotive 88 27 Other 104 44 Commercial real estate 6 1 Total commercial 198 72 Total consumer and commercial finance receivables and loans $ 905 $ 792
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 2017 Annual Report on Form 10-K for additional information. June 30, 2018 December 31, 2017 ($ in millions) Performing Nonperforming Total Performing Nonperforming Total Consumer automotive $ 69,871 $ 602 $ 70,473 $ 67,468 $ 603 $ 68,071 Consumer mortgage Mortgage Finance 13,310 18 13,328 11,632 25 11,657 Mortgage — Legacy 1,716 87 1,803 2,001 92 2,093 Total consumer mortgage 15,026 105 15,131 13,633 117 13,750 Total consumer $ 84,897 $ 707 $ 85,604 $ 81,101 $ 720 $ 81,821
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. June 30, 2018 December 31, 2017 ($ in millions) Pass Criticized (a) Total Pass Criticized (a) Total Commercial and industrial Automotive $ 28,890 $ 2,611 $ 31,501 $ 30,982 $ 2,043 $ 33,025 Other 3,260 767 4,027 2,986 901 3,887 Commercial real estate 4,193 219 4,412 4,023 137 4,160 Total commercial $ 36,343 $ 3,597 $ 39,940 $ 37,991 $ 3,081 $ 41,072 (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 June 30, 2018 Consumer automotive $ 491 $ 480 $ 117 $ 363 $ 42 Consumer mortgage Mortgage Finance 10 10 4 6 — Mortgage — Legacy 223 218 63 155 24 Total consumer mortgage 233 228 67 161 24 Total consumer 724 708 184 524 66 Commercial Commercial and industrial Automotive 88 88 16 72 12 Other 116 104 40 64 15 Commercial real estate 6 6 4 2 — Total commercial 210 198 60 138 27 Total consumer and commercial finance receivables and loans $ 934 $ 906 $ 244 $ 662 $ 93 December 31, 2017 Consumer automotive $ 438 $ 430 $ 91 $ 339 $ 36 Consumer mortgage Mortgage Finance 8 8 4 4 — Mortgage — Legacy 228 223 58 165 27 Total consumer mortgage 236 231 62 169 27 Total consumer 674 661 153 508 63 Commercial Commercial and industrial Automotive 27 27 9 18 3 Other 54 44 10 34 11 Commercial real estate 1 1 — 1 — Total commercial 82 72 19 53 14 Total consumer and commercial finance receivables and loans $ 756 $ 733 $ 172 $ 561 $ 77 (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. 2018 2017 Three months ended June 30, ($ in millions) Average balance Interest income Average balance Interest income Consumer automotive $ 472 $ 7 $ 391 $ 5 Consumer mortgage Mortgage Finance 9 — 8 — Mortgage — Legacy 219 3 238 3 Total consumer mortgage 228 3 246 3 Total consumer 700 10 637 8 Commercial Commercial and industrial Automotive 78 1 54 1 Other 82 — 73 8 Commercial real estate 5 — 6 — Total commercial 165 1 133 9 Total consumer and commercial finance receivables and loans $ 865 $ 11 $ 770 $ 17 2018 2017 Six months ended June 30, ($ in millions) Average balance Interest income Average balance Interest income Consumer automotive $ 462 $ 14 $ 381 $ 10 Consumer mortgage Mortgage Finance 9 — 8 — Mortgage — Legacy 220 5 239 5 Total consumer mortgage 229 5 247 5 Total consumer 691 19 628 15 Commercial Commercial and industrial Automotive 61 2 47 1 Other 66 — 77 8 Commercial real estate 4 — 6 — Total commercial 131 2 130 9 Total consumer and commercial finance receivables and loans $ 822 $ 21 $ 758 $ 24
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. 2018 2017 Three months ended June 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 5,898 $ 107 $ 93 5,762 $ 103 $ 88 Consumer mortgage Mortgage Finance 7 2 2 — — — Mortgage — Legacy 27 6 7 19 3 2 Total consumer mortgage 34 8 9 19 3 2 Total consumer 5,932 115 102 5,781 106 90 Commercial Commercial and industrial Automotive 3 4 4 — — — Other 2 55 51 1 21 21 Total commercial 5 59 55 1 21 21 Total consumer and commercial finance receivables and loans 5,937 $ 174 $ 157 5,782 $ 127 $ 111 2018 2017 Six months ended June 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 12,940 $ 235 $ 203 12,209 $ 218 $ 187 Consumer mortgage Mortgage Finance 8 3 3 1 — — Mortgage — Legacy 89 16 16 72 15 14 Total consumer mortgage 97 19 19 73 15 14 Total consumer 13,037 254 222 12,282 233 201 Commercial Commercial and industrial Automotive 3 4 4 — — — Other 2 55 51 2 44 44 Total commercial 5 59 55 2 44 44 Total consumer and commercial finance receivables and loans 13,042 $ 313 $ 277 12,284 $ 277 $ 245
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 2017 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. 2018 2017 Three months ended June 30, ($ in millions) Number of loans Gross carrying value Charge-off amount Number of loans Gross carrying value Charge-off amount Consumer automotive 2,425 $ 29 $ 17 2,143 $ 25 $ 17 Consumer mortgage Mortgage Finance — — — — — — Mortgage — Legacy 1 — — — — — Total consumer finance receivables and loans 2,426 $ 29 $ 17 2,143 $ 25 $ 17 2018 2017 Six months ended June 30, ($ in millions) Number of loans Gross carrying value Charge-off amount Number of loans Gross carrying value Charge-off amount Consumer automotive 4,751 $ 57 $ 35 4,132 $ 49 $ 33 Consumer mortgage Mortgage Finance — — — 1 1 — Mortgage — Legacy 1 — — — — — Total consumer finance receivables and loans 4,752 $ 57 $ 35 4,133 $ 50 $ 33

Investment in Operating Lease40

Investment in Operating Leases, Net (Tables)	6 Months Ended
	Jun. 30, 2018
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) June 30, 2018 December 31, 2017 Vehicles $ 10,260 $ 10,556 Accumulated depreciation (1,621 ) (1,815 ) Investment in operating leases, net $ 8,639 $ 8,741
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 June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Depreciation expense on operating lease assets (excluding remarketing gains) $ 281 $ 353 $ 572 $ 739 Remarketing gains (16 ) (32 ) (34 ) (29 ) Net depreciation expense on operating lease assets $ 265 $ 321 $ 538 $ 710

Securitizations and Variable 41

Securitizations and Variable Interest Entities (Tables)	6 Months Ended
	Jun. 30, 2018
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 June 30, 2018 On-balance sheet variable interest entities Consumer automotive $ 18,806 (b) $ 8,787 (c) Commercial automotive 9,945 3,595 Off-balance sheet variable interest entities Consumer automotive 28 (d) — $ 1,388 $ 1,416 (e) Commercial other 739 (f) 344 (g) — 968 (h) Total $ 29,518 $ 12,726 $ 1,388 $ 2,384 December 31, 2017 On-balance sheet variable interest entities Consumer automotive $ 17,597 (b) $ 7,677 (c) Commercial automotive 12,550 2,558 Off-balance sheet variable interest entities Consumer automotive 37 (d) — $ 1,964 $ 2,001 (e) Commercial other 592 (f) 248 (g) — 790 (h) Total $ 30,776 $ 10,483 $ 1,964 $ 2,791 (a) Asset values represent the current unpaid principal balance of outstanding consumer finance receivables and loans within the VIEs. (b) Includes $8.5 billion of assets that were not encumbered by VIE beneficial interests held by third parties at both June 30, 2018 , and December 31, 2017 . Ally or consolidated affiliates hold the interests in these assets. (c) Includes $25 million and $29 million of liabilities that were not obligations to third-party beneficial interest holders at June 30, 2018 , and December 31, 2017 , respectively. (d) Represents retained notes and certificated residual interests, of which $27 million and $36 million were classified as held-to-maturity securities at June 30, 2018 , and December 31, 2017 , respectively, and $1 million was classified as other assets at both June 30, 2018 , and December 31, 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. (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 consumer automotive assets (e.g., servicing) that were outstanding during the six months ended June 30, 2018 , and 2017. Additionally, this table contains information regarding cash flows received from and paid to nonconsolidated securitization entities that existed during each period. Six months ended June 30, ($ in millions) Consumer automotive Consumer mortgage 2018 Cash disbursements for repurchases during the period $ (2 ) $ — Servicing fees 10 — Cash flows received on retained interests in securitization entities 9 — Representation and warranty recoveries — 2 2017 Cash proceeds from transfers completed during the period $ 1,187 $ — Cash disbursements for repurchases during the period (a) (491 ) — Servicing fees 18 — Cash flows received on retained interests in securitization entities 10 — Other cash flows 4 — (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 present quantitative information about delinquencies and net credit losses for off-balance sheet securitizations and whole-loan sales where we have continuing involvement. Total amount Amount 60 days or more past due ($ in millions) June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 Off-balance sheet securitization entities Consumer automotive $ 1,388 $ 1,964 $ 12 $ 16 Total off-balance sheet securitization entities 1,388 1,964 12 16 Whole-loan sales (a) 964 1,399 3 4 Total $ 2,352 $ 3,363 $ 15 $ 20 (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 June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Off-balance sheet securitization entities Consumer automotive $ 2 $ 3 $ 5 $ 6 Total off-balance sheet securitization entities 2 3 5 6 Whole-loan sales (a) — 1 1 2 Total $ 2 $ 4 $ 6 $ 8 (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)	6 Months Ended
	Jun. 30, 2018
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 net investment in operating leases outstanding were as follows. ($ in millions) June 30, 2018 December 31, 2017 On-balance sheet automotive finance loans and leases Consumer automotive $ 69,701 $ 67,631 Commercial automotive 35,645 37,058 Operating leases 8,613 8,682 Other 111 121 Off-balance sheet automotive finance loans Securitizations 1,392 1,977 Whole-loan sales 969 1,409 Total serviced automotive finance loans and leases $ 116,431 $ 116,878

Other Assets (Tables)

Other Assets (Tables)	6 Months Ended
	Jun. 30, 2018
Other Assets [Abstract]
Schedule of Other Assets [Table Text Block]	The components of other assets were as follows. ($ in millions) June 30, 2018 December 31, 2017 Property and equipment at cost $ 1,161 $ 1,064 Accumulated depreciation (648 ) (608 ) Net property and equipment 513 456 Nonmarketable equity investments (a) 1,276 1,233 Restricted cash collections for securitization trusts (b) 796 812 Accrued interest and rent receivables 548 550 Net deferred tax assets 455 461 Other accounts receivable 289 116 Goodwill (c) 240 240 Restricted cash and cash equivalents (d) 116 94 Cash reserve deposits held for securitization trusts (e) 103 111 Fair value of derivative contracts in receivable position (f) 63 39 Cash collateral placed with counterparties 35 29 Other assets 1,580 1,522 Total other assets $ 6,014 $ 5,663 (a) Includes investments in FHLB stock of $790 million and $745 million at June 30, 2018 , and December 31, 2017, respectively; FRB stock of $447 million and $445 million at June 30, 2018 , and December 31, 2017, respectively; and equity securities without a readily determinable fair value of $39 million at June 30, 2018 , measured at cost with adjustments for impairment and observable changes in price. During the three months and six months ended June 30, 2018 , we recorded $1 million in impairment related to equity securities without a readily determinable fair value. (b) Represents cash collections from customer payments on securitized receivables. These funds are distributed to investors as payments on the related secured debt. (c) Includes goodwill of $27 million within our Insurance operations at both June 30, 2018 , and December 31, 2017 ; $193 million within Corporate and Other at both June 30, 2018 , and December 31, 2017 ; and $20 million within Automotive Finance operations at both June 30, 2018 , and December 31, 2017 . No changes to the carrying amount of goodwill were recorded during the six months ended June 30, 2018 . (d) Primarily represents a number of arrangements with third parties where certain restrictions are placed on balances we hold due to collateral agreements associated with operational processes with a third-party bank, or letter of credit arrangements and corresponding collateral requirements. (e) Represents credit enhancement in the form of cash reserves for various securitization transactions. (f) For additional information on derivative instruments and hedging activities, refer to Note 18 .

Deposit Liabilities (Tables)

Deposit Liabilities (Tables)	6 Months Ended
	Jun. 30, 2018
Deposits [Abstract]
Deposit Liabilities, Type [Table Text Block]	Deposit liabilities consisted of the following. ($ in millions) June 30, 2018 December 31, 2017 Noninterest-bearing deposits $ 153 $ 108 Interest-bearing deposits Savings and money market checking accounts 50,958 49,267 Certificates of deposit 47,617 43,869 Dealer deposits 6 12 Total deposit liabilities $ 98,734 $ 93,256

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Schedule of Short-term Debt [Table Text Block]	The following table presents the composition of our short-term borrowings portfolio. June 30, 2018 December 31, 2017 ($ in millions) Unsecured Secured (a) Total Unsecured Secured (a) Total Demand notes $ 2,666 $ — $ 2,666 $ 3,171 $ — $ 3,171 Federal Home Loan Bank — 3,475 3,475 — 7,350 7,350 Financial instruments sold under agreements to repurchase — 967 967 — 892 892 Total short-term borrowings $ 2,666 $ 4,442 $ 7,108 $ 3,171 $ 8,242 $ 11,413 (a) Refer to the section below titled Long-term Debt for further details on assets restricted as collateral for payment of the related debt.
Long-term Debt [Text Block]	The following table presents the composition of our long-term debt portfolio. June 30, 2018 December 31, 2017 ($ in millions) Unsecured Secured Total Unsecured Secured Total Long-term debt Due within one year $ 2,740 $ 8,016 $ 10,756 $ 3,482 $ 7,499 $ 10,981 Due after one year (a) 11,139 25,334 36,473 11,909 21,128 33,037 Fair value adjustment (b) 168 (69 ) 99 240 (32 ) 208 Total long-term debt (c) $ 14,047 $ 33,281 $ 47,328 $ 15,631 $ 28,595 $ 44,226 (a) Includes $2.6 billion of trust preferred securities at both June 30, 2018 , and December 31, 2017. (b) Represents the basis adjustment associated with the application of hedge accounting on certain of our long-term debt positions. Refer to Note 18 for additional information. (c) Includes advances from the FHLB of Pittsburgh of $14.7 billion and $10.3 billion at June 30, 2018 , and December 31, 2017, respectively.
Scheduled of Maturities of Long-term Debt [Table Text Block]	The following table presents the scheduled remaining maturity of long-term debt at June 30, 2018 , assuming no early redemptions will occur. The actual payment of secured debt may vary based on the payment activity of the related pledged assets. ($ in millions) 2018 2019 2020 2021 2022 2023 and thereafter Fair value adjustment Total Unsecured Long-term debt $ 1,991 $ 1,681 $ 2,251 $ 663 $ 1,066 $ 7,414 $ 168 $ 15,234 Original issue discount (52 ) (38 ) (39 ) (43 ) (47 ) (968 ) — (1,187 ) Total unsecured 1,939 1,643 2,212 620 1,019 6,446 168 14,047 Secured Long-term debt 3,356 7,995 7,430 8,484 4,562 1,523 (69 ) 33,281 Total long-term debt $ 5,295 $ 9,638 $ 9,642 $ 9,104 $ 5,581 $ 7,969 $ 99 $ 47,328
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. June 30, 2018 December 31, 2017 ($ in millions) Total (a) Ally Bank Total (a) Ally Bank Investment securities (b) $ 7,902 $ 6,995 $ 8,371 $ 7,443 Mortgage assets held-for-investment and lending receivables 14,943 14,943 13,579 13,579 Consumer automotive finance receivables 18,965 9,621 19,787 6,200 Commercial automotive finance receivables 14,252 14,211 16,567 16,472 Operating leases 267 — 457 — Total assets restricted as collateral (c) (d) $ 56,329 $ 45,770 $ 58,761 $ 43,694 Secured debt $ 37,723 (e) $ 27,990 $ 36,837 (e) $ 23,278 (a) Ally Bank is a component of the total column. (b) A portion of the restricted investment securities at June 30, 2018 , and December 31, 2017 , 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 $26.3 billion and $25.2 billion at June 30, 2018 , and December 31, 2017 , 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 $2.4 billion and $2.3 billion at June 30, 2018 , and December 31, 2017 , respectively. These assets were composed of consumer automotive finance receivables and loans. 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 11 for additional information. (e) Includes $4.4 billion and $8.2 billion of short-term borrowings at June 30, 2018 , and December 31, 2017 , respectively
Schedule Of Committed Funding Facilities [Table Text Block]	Outstanding Unused capacity (a) Total capacity ($ in millions) June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 Bank funding Secured $ 2,500 $ 1,785 $ — $ 890 $ 2,500 $ 2,675 Parent funding Secured 3,855 6,330 2,870 2,920 6,725 9,250 Total committed facilities $ 6,355 $ 8,115 $ 2,870 $ 3,810 $ 9,225 $ 11,925 (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.

Accrued Expenses and Other Li46

Accrued Expenses and Other Liabilities (Tables)	6 Months Ended
	Jun. 30, 2018
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) June 30, 2018 December 31, 2017 Accounts payable $ 369 $ 746 Employee compensation and benefits 188 248 Reserves for insurance losses and loss adjustment expenses 149 140 Fair value of derivative contracts in payable position (a) 65 41 Cash collateral received from counterparties 39 17 Deferred revenue 28 32 Other liabilities 673 556 Total accrued expenses and other liabilities $ 1,511 $ 1,780 (a) For additional information on derivative instruments and hedging activities, refer to Note 18 .

Accumulated Other Comprehensi47

Accumulated Other Comprehensive Loss (Tables)	6 Months Ended
	Jun. 30, 2018
Other Comprehensive Income (Loss), Net of Tax [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. ($ 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 Balance at December 31, 2016 $ (273 ) $ 14 $ 8 $ (90 ) $ (341 ) 2017 net change 96 — 1 (1 ) 96 Balance at June 30, 2017 $ (177 ) $ 14 $ 9 $ (91 ) $ (245 ) Balance at December 31, 2017, before cumulative effect of adjustments $ (173 ) $ 16 $ 11 $ (89 ) $ (235 ) Cumulative effect of changes in accounting principles, net of tax (c) Adoption of Accounting Standards Update 2016-01 27 — — — 27 Adoption of Accounting Standards Update 2018-02 (40 ) 4 — (6 ) (42 ) Balance at January 1, 2018, after cumulative effect of adjustments (186 ) 20 11 (95 ) (250 ) 2018 net change (412 ) (1 ) 17 (2 ) (398 ) Balance at June 30, 2018 $ (598 ) $ 19 $ 28 $ (97 ) $ (648 ) (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 18 . (c) Refer to the section titled Recently Adopted Accounting Standards in Note 1 for additional information.
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 June 30, 2018 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized losses arising during the period $ (95 ) $ 22 $ (73 ) Less: Net realized gains reclassified to income from continuing operations 1 (a) — (b) 1 Net change (96 ) 22 (74 ) Translation adjustments Net unrealized losses arising during the period (3 ) 1 (2 ) Net investment hedges (c) Net unrealized gains arising during the period 3 (1 ) 2 Cash flow hedges (c) Net unrealized gains arising during the period 5 (2 ) 3 Defined benefit pension plans Net unrealized gains arising during the period 1 — 1 Other comprehensive loss $ (90 ) $ 20 $ (70 ) (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 18 . Three months ended June 30, 2017 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 132 $ (37 ) $ 95 Less: Net realized gains reclassified to income from continuing operations 23 (a) (3 ) (b) 20 Net change 109 (34 ) 75 Translation adjustments Net unrealized gains arising during the period 4 (1 ) 3 Net investment hedges (c) Net unrealized losses arising during the period (4 ) 1 (3 ) Cash flow hedges (c) Net unrealized gains arising during the period 1 — 1 Other comprehensive income $ 110 $ (34 ) $ 76 (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 18 . Six months ended June 30, 2018 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized losses arising during the period $ (531 ) $ 125 $ (406 ) Less: Net realized gains reclassified to income from continuing operations 7 (a) (1 ) (b) 6 Net change (538 ) 126 (412 ) Translation adjustments Net unrealized losses arising during the period (8 ) 2 (6 ) Net investment hedges (c) Net unrealized gains arising during the period 7 (2 ) 5 Cash flow hedges (c) Net unrealized gains arising during the period 23 (6 ) 17 Defined benefit pension plans Net unrealized losses arising during the period (2 ) — (2 ) Other comprehensive loss $ (518 ) $ 120 $ (398 ) (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 18 . Six months ended June 30, 2017 ($ in millions) Before tax Tax effect After tax Investment securities Net unrealized gains arising during the period $ 183 $ (42 ) $ 141 Less: Net realized gains reclassified to income from continuing operations 50 (a) (5 ) (b) 45 Net change 133 (37 ) 96 Translation adjustments Net unrealized gains arising during the period 6 (2 ) 4 Net investment hedges (c) Net unrealized losses arising during the period (6 ) 2 (4 ) Cash flow hedges (c) Net unrealized gains arising during the period 1 — 1 Defined benefit pension plans Net unrealized losses arising during the period (1 ) — (1 ) Other comprehensive income $ 133 $ (37 ) $ 96 (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 18 .

Earnings per Common Share (Tabl

Earnings per Common Share (Tables)	6 Months Ended
	Jun. 30, 2018
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 June 30, Six months ended June 30, ($ in millions, except per share data; shares in thousands) (a) 2018 2017 2018 2017 Net income from continuing operations attributable to common stockholders $ 348 $ 254 $ 600 $ 467 Income (loss) from discontinued operations, net of tax 1 (2 ) (1 ) (1 ) Net income attributable to common stockholders $ 349 $ 252 $ 599 $ 466 Basic weighted-average common shares outstanding (b) 430,628 457,891 433,405 461,904 Diluted weighted-average common shares outstanding (b) 432,554 458,819 435,727 462,802 Basic earnings per common share Net income from continuing operations $ 0.81 $ 0.55 $ 1.38 $ 1.01 Loss from discontinued operations, net of tax — (0.01 ) — — Net income $ 0.81 $ 0.55 $ 1.38 $ 1.01 Diluted earnings per common share Net income from continuing operations $ 0.80 $ 0.55 $ 1.38 $ 1.01 Loss from discontinued operations, net of tax — (0.01 ) — — Net income $ 0.81 $ 0.55 $ 1.37 $ 1.01 (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 six months ended June 30, 2018 , and 2017 .

Regulatory Capital and Other 49

Regulatory Capital and Other Regulatory Matters (Tables)	6 Months Ended
	Jun. 30, 2018
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. June 30, 2018 December 31, 2017 Required minimum (a) Well-capitalized minimum ($ in millions) Amount Ratio Amount Ratio Capital ratios Common Equity Tier 1 (to risk-weighted assets) Ally Financial Inc. $ 13,265 9.37 % $ 13,237 9.53 % 4.50 % (b) Ally Bank 16,591 13.65 17,059 15.04 4.50 6.50 % Tier 1 (to risk-weighted assets) Ally Financial Inc. $ 15,698 11.09 % $ 15,628 11.25 % 6.00 % 6.00 % Ally Bank 16,591 13.65 17,059 15.04 6.00 8.00 Total (to risk-weighted assets) Ally Financial Inc. $ 17,926 12.66 % $ 17,974 12.94 % 8.00 % 10.00 % Ally Bank 17,557 14.45 17,886 15.77 8.00 10.00 Tier 1 leverage (to adjusted quarterly average assets) (c) Ally Financial Inc. $ 15,698 9.21 % $ 15,628 9.53 % 4.00 % (b) Ally Bank 16,591 11.50 17,059 12.87 4.00 5.00 % (a) In addition to the minimum risk-based capital requirements for common equity Tier 1 capital, Tier 1 capital, and total capital ratios, Ally and Ally Bank were required to maintain a minimum capital conservation buffer of 1.875% and 1.25% at June 30, 2018, and December 31, 2017, respectively, which ultimately increases to 2.5% on January 1, 2019. (b) Currently, there is no ratio component for determining whether a BHC is “well-capitalized.” (c) Federal regulatory reporting guidelines require the calculation of adjusted quarterly average assets using a daily average methodology.
Schedule of Common Share Repurchase Activity [Table Text Block]	The following table presents information related to our common stock for each quarter since the commencement of our common stock repurchase programs and initiation of a quarterly cash dividend on common stock. Common stock repurchased during period (a) Number of common shares outstanding Cash dividends declared per common share (b) ($ in millions, except per share data; shares in thousands) Approximate dollar value Number of shares Beginning of period End of period 2016 Third quarter $ 159 8,298 483,753 475,470 $ 0.08 Fourth quarter 167 8,745 475,470 467,000 0.08 2017 First quarter $ 169 8,097 467,000 462,193 $ 0.08 Second quarter 204 10,485 462,193 452,292 0.08 Third quarter 190 8,507 452,292 443,796 0.12 Fourth quarter 190 7,033 443,796 437,054 0.12 2018 First quarter $ 185 6,473 437,054 432,691 $ 0.13 Second quarter 195 7,280 432,691 425,752 0.13 (a) Includes shares of common stock withheld to cover income taxes owed by participants in our share-based incentive plans. (b) On July 13, 2018 , the Ally Board of Directors (the Board) declared a quarterly cash dividend of $0.15 per share on all common stock, payable on August 15, 2018 . Refer to Note 25 for further information regarding this common stock dividend.

Derivative Instruments and He50

Derivative Instruments and Hedging Activities (Tables)	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position [Table Text Block]	The following table summarizes the amounts of derivative instruments reported on our Condensed Consolidated Balance Sheet . The 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. 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 on our Condensed Consolidated Balance Sheet . 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. June 30, 2018 December 31, 2017 Derivative contracts in a Notional amount Derivative contracts in a Notional amount ($ in millions) receivable position payable position receivable position payable position Derivatives designated as accounting hedges Interest rate contracts Swaps $ — $ — $ 28,840 $ — $ — $ 6,915 Foreign exchange contracts Forwards — 1 145 — 1 136 Total derivatives designated as accounting hedges — 1 28,985 — 1 7,051 Derivatives not designated as accounting hedges Interest rate contracts Futures and forwards — — 9 — — 23 Written options 1 62 6,760 1 39 8,327 Purchased options 62 — 6,694 38 — 8,237 Total interest rate risk 63 62 13,463 39 39 16,587 Foreign exchange contracts Futures and forwards — 1 193 — 1 124 Total foreign exchange risk — 1 193 — 1 124 Equity contracts Written options — 1 — — — — Total equity risk — 1 — — — — Total derivatives not designated as accounting hedges 63 64 13,656 39 40 16,711 Total derivatives $ 63 $ 65 $ 42,641 $ 39 $ 41 $ 23,762
Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block]	The following table presents amounts recorded on our Condensed Consolidated Balance Sheet related to cumulative basis adjustments for fair value hedges. ($ in millions) Carrying amount of the hedged items Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged items Total Discontinued (a) June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 Assets Available-for-sale securities (b) $ 1,435 $ 173 $ (3 ) $ 2 $ (2 ) $ 2 Finance receivables and loans, net (c) 41,383 2,305 (40 ) 18 11 19 Liabilities Long-term debt $ 14,959 $ 14,640 $ 99 $ 208 $ 95 $ 235 (a) Represents the fair value hedging adjustment on qualifying hedges for which the hedging relationship was discontinued. This represents a subset of the amounts reported in the total hedging adjustment. (b) The carrying amount of hedged available-for-sale securities is presented above using amortized cost. Refer to Note 6 for a reconciliation of the amortized cost and fair value of available-for-sale securities. (c) The hedged item represents the carrying value of the hedged portfolio of assets. The amount that is identified as the last of layer in the hedge relationship is $17.7 billion as of June 30, 2018 . The basis adjustment associated with the last-of-layer relationship is a $51 million liability as of June 30, 2018 , which would be allocated across the entire remaining closed pool upon termination or maturity of the hedge relationship. A last-of-layer hedge strategy did not exist at December 31, 2017 .
Derivative Instruments, Gain (Loss) [Table Text Block]	The following table summarizes the location and amounts of gains and losses on derivative instruments not designated as accounting hedges reported in our Condensed Consolidated Statement of Comprehensive Income . Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Gain (loss) recognized in earnings Interest rate contracts Gain on mortgage and automotive loans, net $ — $ 1 $ — $ 1 Other income, net of losses (2 ) (1 ) — (3 ) Total interest rate contracts (2 ) — — (2 ) Foreign exchange contracts Other income, net of losses 6 (3 ) 6 (4 ) Total foreign exchange contracts 6 (3 ) 6 (4 ) Gain (loss) recognized in earnings $ 4 $ (3 ) $ 6 $ (6 )
Derivative Instruments Designated as FV Hedges, Gain (Loss) [Table Text Block]	The following table summarizes the location and amounts of gains and losses on derivative instruments designated as fair value hedges reported in our Condensed Consolidated Statement of Comprehensive Income . We had no gains or losses on derivative instruments designated as cash flow hedges for the periods shown. Interest and fees on finance receivables and loans Interest and dividends on investment securities and other earning assets Interest on long-term debt Three months ended June 30, ($ in millions) 2018 2017 2018 2017 2018 2017 Gain (loss) on fair value hedging relationships Interest rate contracts Hedged fixed-rate unsecured debt $ — $ — $ — $ — $ 8 $ (21 ) Derivatives designated as hedging instruments on fixed-rate unsecured debt — — — — (8 ) 21 Hedged fixed-rate FHLB advances — — — — 10 1 Derivatives designated as hedging instruments on fixed-rate FHLB advances — — — — (10 ) (1 ) Hedged available-for-sale securities — — (2 ) 2 — — Derivatives designated as hedging instruments on available-for-sale securities — — 2 (2 ) — — Hedged fixed-rate retail automotive loans (6 ) 1 — — — — Derivatives designated as hedging instruments on fixed-rate retail automotive loans 6 (1 ) — — — — Total loss on fair value hedging relationships $ — $ — $ — $ — $ — $ — Total amounts presented in the Condensed Consolidated Statement of Comprehensive Income $ 1,647 $ 1,447 $ 188 $ 146 $ 434 $ 417 Interest and fees on finance receivables and loans Interest and dividends on investment securities and other earning assets Interest on long-term debt Six months ended June 30, ($ in millions) 2018 2017 2018 2017 2018 2017 Gain (loss) on fair value hedging relationships Interest rate contracts Hedged fixed-rate unsecured debt $ — $ — $ — $ — $ 44 $ (23 ) Derivatives designated as hedging instruments on fixed-rate unsecured debt — — — — (43 ) 24 Hedged fixed-rate FHLB advances — — — — 43 — Derivatives designated as hedging instruments on fixed-rate FHLB advances — — — — (43 ) — Hedged available-for-sale securities — — (5 ) 2 — — Derivatives designated as hedging instruments on available-for-sale securities — — 5 (2 ) — — Hedged fixed-rate retail automotive loans (51 ) (3 ) — — — — Derivatives designated as hedging instruments on fixed-rate retail automotive loans 51 1 — — — — Total (loss) gain on fair value hedging relationships $ — $ (2 ) $ — $ — $ 1 $ 1 Total amounts presented in the Condensed Consolidated Statement of Comprehensive Income $ 3,190 $ 2,815 $ 364 $ 280 $ 845 $ 841
Schedule of Derivative Instruments [Table Text Block]	The following table summarizes the location and amounts of gains and losses related to interest and amortization on derivative instruments designated as fair value and cash flow hedges reported in our Condensed Consolidated Statement of Comprehensive Income . Interest and fees on finance receivables and loans Interest on long-term debt Three months ended June 30, ($ in millions) 2018 2017 2018 2017 Gain (loss) on fair value hedging relationships Interest rate contracts Amortization of deferred unsecured debt basis adjustments $ — $ — $ 14 $ 20 Interest for qualifying accounting hedges of unsecured debt — — 1 7 Amortization of deferred secured debt basis adjustments (FHLB advances) — — (5 ) — Interest for qualifying accounting hedges of secured debt (FHLB advances) — — 2 — Amortization of deferred loan basis adjustments (4 ) (6 ) — — Interest for qualifying accounting hedges of retail automotive loans held-for-investment 5 — — — Total (loss) gain on fair value hedging relationships 1 (6 ) 12 27 Gain on cash flow hedging relationships Interest rate contracts Interest for qualifying accounting hedges of variable-rate borrowings — — 2 — Total gain on cash flow hedging relationships $ — $ — $ 2 $ — Interest and fees on finance receivables and loans Interest and dividends on investment securities and other earning assets Interest on long-term debt Six months ended June 30, ($ in millions) 2018 2017 2018 2017 2018 2017 Gain (loss) on fair value hedging relationships Interest rate contracts Amortization of deferred unsecured debt basis adjustments $ — $ — $ — $ — $ 29 $ 40 Interest for qualifying accounting hedges of unsecured debt — — — — 4 12 Amortization of deferred secured debt basis adjustments (FHLB advances) — — — — (6 ) (1 ) Interest for qualifying accounting hedges of secured debt (FHLB advances) — — — — 4 — Interest for qualifying accounting hedges of available-for-sale securities — — (1 ) — — — Amortization of deferred loan basis adjustments (8 ) (11 ) — — — — Interest for qualifying accounting hedges of retail automotive loans held-for-investment (2 ) (1 ) — — — — Total (loss) gain on fair value hedging relationships (10 ) (12 ) (1 ) — 31 51 Gain on cash flow hedging relationships Interest rate contracts Interest for qualifying accounting hedges of variable-rate borrowings — — — — 3 — Total gain on cash flow hedging relationships $ — $ — $ — $ — $ 3 $ —
Schedule of Derivative Instruments, Effect on Other Comprehensive Income [Table Text Block]	The following table summarizes the effect of cash flow hedges on accumulated other comprehensive loss. Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Interest rate contracts Gain recognized in other comprehensive loss $ 5 $ 1 $ 23 $ 1 The following table summarizes the effect of net investment hedges on accumulated other comprehensive loss and the Condensed Consolidated Statement of Comprehensive Income . Three months ended June 30, Six months ended June 30, ($ in millions) 2018 2017 2018 2017 Foreign exchange contracts (a) (b) Gain (loss) recognized in other comprehensive loss $ 3 $ (4 ) $ 7 $ (6 ) (a) There were no amounts excluded from effectiveness testing for the three months and six months ended June 30, 2018 , or 2017 . (b) Gains and losses reclassified from accumulated other comprehensive loss are reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income . There were no amounts reclassified for the three months and six months ended June 30, 2018 , or 2017 .

Fair Value (Tables)

Fair Value (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on a 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 June 30, 2018 ($ in millions) Level 1 Level 2 Level 3 Total Assets Investment securities Equity securities (a) $ 509 $ — $ 12 $ 521 Available-for-sale securities Debt securities U.S. Treasury 1,874 — — 1,874 U.S. States and political subdivisions — 851 — 851 Foreign government 7 147 — 154 Agency mortgage-backed residential — 15,066 — 15,066 Mortgage-backed residential — 2,625 — 2,625 Mortgage-backed commercial — 642 — 642 Asset-backed — 868 — 868 Corporate debt — 1,216 — 1,216 Total available-for-sale securities 1,881 21,415 — 23,296 Mortgage loans held-for-sale (b) — — 13 13 Interests retained in financial asset sales — — 4 4 Derivative contracts in a receivable position Interest rate — 62 1 63 Total derivative contracts in a receivable position — 62 1 63 Total assets $ 2,390 $ 21,477 $ 30 $ 23,897 Liabilities Accrued expenses and other liabilities Derivative contracts in a payable position Interest rate $ — $ 62 $ — $ 62 Foreign currency — 2 — 2 Other 1 — — 1 Total derivative contracts in a payable position 1 64 — 65 Total liabilities $ 1 $ 64 $ — $ 65 (a) Our investment in any one industry did not exceed 15% . (b) Carried at fair value due to fair value option elections. Recurring fair value measurements December 31, 2017 ($ in millions) Level 1 Level 2 Level 3 Total Assets Investment securities Equity securities (a) $ 518 $ — $ — $ 518 Available-for-sale securities Debt securities U.S. Treasury 1,777 — — 1,777 U.S. States and political subdivisions — 854 — 854 Foreign government 8 146 — 154 Agency mortgage-backed residential — 14,291 — 14,291 Mortgage-backed residential — 2,494 — 2,494 Mortgage-backed commercial — 541 — 541 Asset-backed — 936 — 936 Corporate debt — 1,256 — 1,256 Total available-for-sale securities 1,785 20,518 — 22,303 Mortgage loans held-for-sale (b) — — 13 13 Interests retained in financial asset sales — — 5 5 Derivative contracts in a receivable position Interest rate — 38 1 39 Total derivative contracts in a receivable position — 38 1 39 Total assets $ 2,303 $ 20,556 $ 19 $ 22,878 Liabilities Accrued expenses and other liabilities Derivative contracts in a payable position Interest rate $ — $ 39 $ — $ 39 Foreign currency — 2 — 2 Total derivative contracts in a payable position — 41 — 41 Total liabilities $ — $ 41 $ — $ 41 (a) Our investment in any one industry did not exceed 14% . (b) Carried at fair value due to fair value option elections.
Fair Value, Assets Measured on a Recurring Basis, Unobservable Input Reconciliation [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 June 30, 2018 Net unrealized gains included in earnings still held at June 30, 2018 ($ in millions) Fair value at April 1, 2018 included in earnings included in OCI Purchases Sales Issuances Settlements Assets Equity securities $ 12 $ — $ — $ — $ — $ — $ — $ 12 $ — Mortgage loans held-for-sale (a) 7 1 (b) — 73 (68 ) — — 13 — Other assets Interests retained in financial asset sales 5 — — — — — (1 ) 4 — Derivative assets 1 — — — — — — 1 — Total assets $ 25 $ 1 $ — $ 73 $ (68 ) $ — $ (1 ) $ 30 $ — (a) Carried at fair value due to fair value option elections. (b) Reported as gain on mortgage and automotive loans, net, in the Condensed Consolidated Statement of Comprehensive Income . Level 3 recurring fair value measurements Fair value at April 1, 2017 Net realized/unrealized gains Purchases Sales Issuances Settlements Fair value at June 30, 2017 Net unrealized gains included in earnings still held at June 30, 2017 ($ in millions) included in earnings included in OCI Assets Mortgage loans held-for-sale (a) $ 1 $ — $ — $ 20 $ (18 ) $ — $ — $ 3 $ — Other assets Interests retained in financial asset sales 31 1 (b) — — 4 — (31 ) 5 — Derivative assets — 1 (c) — — — — — 1 1 Total assets $ 32 $ 2 $ — $ 20 $ (14 ) $ — $ (31 ) $ 9 $ 1 (a) Carried at fair value due to fair value option elections. (b) Reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income . (c) Reported as gain on mortgage and automotive loans, net, in the Condensed Consolidated Statement of Comprehensive Income . Level 3 recurring fair value measurements Net realized/unrealized (losses) gains Fair value at June 30, 2018 Net unrealized losses included in earnings still held at June 30, 2018 ($ in millions) Fair value at Jan. 1, 2018 included in earnings included in OCI Purchases Sales Issuances Settlements Assets Equity securities (a) $ 19 $ (4 ) (b) $ — $ — $ — $ — $ (3 ) $ 12 $ (5 ) Mortgage loans held-for-sale (c) 13 2 (d) — 132 (134 ) — — 13 — Other assets Interests retained in financial asset sales 5 — — — — — (1 ) 4 — Derivative assets 1 — — — — — — 1 — Total assets $ 38 $ (2 ) $ — $ 132 $ (134 ) $ — $ (4 ) $ 30 $ (5 ) (a) In connection with our adoption of ASU 2016-01 on January 1, 2018, certain of our equity securities previously measured using the cost method of accounting are now measured at fair value on a recurring basis, and have been categorized as Level 3 within the fair value hierarchy. Accordingly, the fair value of such investments has been included in the opening balance of the reconciliation above. (b) Reported as other loss on investments, net, in the Condensed Consolidated Statement of Comprehensive Income . (c) Carried at fair value due to fair value option elections. (d) Reported as gain on mortgage and automotive loans, net, in the Condensed Consolidated Statement of Comprehensive Income . Level 3 recurring fair value measurements Fair value at Jan. 1, 2017 Net realized/unrealized gains Purchases Sales Issuances Settlements Fair value at June 30, 2017 Net unrealized gains included in earnings still held at June 30, 2017 ($ in millions) included in earnings included in OCI Assets Mortgage loans held-for-sale (a) $ — $ — $ — $ 23 $ (20 ) $ — $ — $ 3 $ — Other assets Interests retained in financial asset sales 29 1 (b) — — 8 — (33 ) 5 — Derivative assets — 1 (c) — — — — — 1 1 Total assets $ 29 $ 2 $ — $ 23 $ (12 ) $ — $ (33 ) $ 9 $ 1 (a) Carried at fair value due to fair value option elections. (b) Reported as other income, net of losses, in the Condensed Consolidated Statement of Comprehensive Income . (c) Reported as gain on mortgage and automotive loans, net, 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 June 30, 2018 ($ in millions) Level 1 Level 2 Level 3 Total Assets Loans held-for-sale, net $ — $ — $ 315 $ 315 $ — n/m (a) Commercial finance receivables and loans, net (b) Automotive — — 62 62 (12 ) n/m (a) Other — — 50 50 (15 ) n/m (a) Total commercial finance receivables and loans, net — — 112 112 (27 ) n/m (a) Other assets Repossessed and foreclosed assets (c) — — 13 13 (1 ) n/m (a) Total assets $ — $ — $ 440 $ 440 $ (28 ) 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 2018 . 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 (loss) included in earnings December 31, 2017 ($ in millions) Level 1 Level 2 Level 3 Total Assets Loans held-for-sale, net $ — $ — $ 77 $ 77 $ — n/m (a) Commercial finance receivables and loans, net (b) Automotive — — 20 20 (3 ) n/m (a) Other — — 22 22 (12 ) n/m (a) Total commercial finance receivables and loans, net — — 42 42 (15 ) n/m (a) Other assets Repossessed and foreclosed assets (c) — — 14 14 (1 ) n/m (a) Other — — 3 3 — n/m (a) Total assets $ — $ — $ 136 $ 136 $ (16 ) 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.
Financial Instruments Disclosure [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 June 30, 2018 , and December 31, 2017 . Estimated fair value ($ in millions) Carrying value Level 1 Level 2 Level 3 Total June 30, 2018 Financial assets Held-to-maturity securities $ 2,089 $ — $ 2,007 $ — $ 2,007 Loans held-for-sale, net 315 — — 315 315 Finance receivables and loans, net 124,287 — — 125,846 125,846 Nonmarketable equity investments 1,237 — 1,237 — 1,237 Financial liabilities Deposit liabilities (a) $ 49,617 $ — $ — $ 49,493 $ 49,493 Short-term borrowings 7,108 — — 7,112 7,112 Long-term debt 47,328 — 28,040 21,094 49,134 December 31, 2017 Financial assets Held-to-maturity securities $ 1,899 $ — $ 1,865 $ — $ 1,865 Loans held-for-sale, net 95 — — 95 95 Finance receivables and loans, net 121,617 — — 123,302 123,302 Nonmarketable equity investments 1,233 — 1,190 49 1,239 Financial liabilities Deposit liabilities (a) $ 45,869 $ — $ — $ 45,827 $ 45,827 Short-term borrowings 11,413 — — 11,417 11,417 Long-term debt 44,226 — 27,807 18,817 46,624 (a) In connection with our adoption of ASU 2016-01 on January 1, 2018, deposit liabilities with no defined or contractual maturities are no longer included in the table above. Amounts for December 31, 2017, have been adjusted to conform to the current presentation and exclude $47.4 billion and $45.2 billion of deposit liabilities with no defined or contractual maturities from the carrying value and Level 3 fair value, respectively. Refer to Note 12 for information regarding the composition of our deposits portfolio, and Note 1 for further information regarding recently adopted accounting standards.

Offsetting Assets and Liabili52

Offsetting Assets and Liabilities (Tables)	6 Months Ended
	Jun. 30, 2018
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 on the Condensed Consolidated Balance Sheet Net amounts of assets/liabilities presented on the Condensed Consolidated Balance Sheet Gross amounts not offset on the Condensed Consolidated Balance Sheet June 30, 2018 ($ in millions) Financial instruments Collateral (a) (b) (c) Net amount Assets Derivative assets in net asset positions $ 62 $ — $ 62 $ — $ — $ 62 Derivative assets with no offsetting arrangements 1 — 1 — — 1 Total assets (d) $ 63 $ — $ 63 $ — $ — $ 63 Liabilities Derivative liabilities in net liability positions (d) $ 65 $ — $ 65 $ — $ (1 ) $ 64 Securities sold under agreements to repurchase (e) 967 — 967 — (967 ) — Total liabilities $ 1,032 $ — $ 1,032 $ — $ (968 ) $ 64 (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. $11 million of noncash derivative collateral pledged to us was excluded at June 30, 2018 . 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 $11 million at June 30, 2018 . We have not sold or pledged any of the noncash collateral received under these agreements as of June 30, 2018 . (d) For additional information on derivative instruments and hedging activities, refer to Note 18 . (e) For additional information on securities sold under agreements to repurchase, refer to Note 13 . Gross amounts of recognized assets/liabilities Gross amounts offset on the Condensed Consolidated Balance Sheet Net amounts of assets/liabilities presented on the Condensed Consolidated Balance Sheet Gross amounts not offset on the Condensed Consolidated Balance Sheet December 31, 2017 ($ in millions) Financial instruments Collateral (a) (b) (c) Net amount Assets Derivative assets in net asset positions $ 38 $ — $ 38 $ — $ — $ 38 Derivative assets with no offsetting arrangements 1 — 1 — — 1 Total assets (d) $ 39 $ — $ 39 $ — $ — $ 39 Liabilities Derivative liabilities in net liability positions (d) $ 41 $ — $ 41 $ — $ (1 ) $ 40 Securities sold under agreements to repurchase (e) 892 — 892 — (892 ) — Total liabilities $ 933 $ — $ 933 $ — $ (893 ) $ 40 (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 December 31, 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 December 31, 2017. We have not sold or pledged any of the noncash collateral received under these agreements as of December 31, 2017. (d) For additional information on derivative instruments and hedging activities, refer to Note 18 . (e) For additional information on securities sold under agreements to repurchase, refer to Note 13 .

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2018
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 June 30, ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated (a) 2018 Net financing revenue and other interest income $ 925 $ 13 $ 44 $ 57 $ 55 $ 1,094 Other revenue 63 266 2 14 19 364 Total net revenue 988 279 46 71 74 1,458 Provision for loan losses 170 — — (6 ) (6 ) 158 Total noninterest expense 436 268 32 19 84 839 Income (loss) from continuing operations before income tax expense $ 382 $ 11 $ 14 $ 58 $ (4 ) $ 461 Total assets $ 114,915 $ 7,634 $ 13,385 $ 4,458 $ 30,953 $ 171,345 2017 Net financing revenue and other interest income $ 932 $ 14 $ 32 $ 48 $ 41 $ 1,067 Other revenue 107 245 1 10 25 388 Total net revenue 1,039 259 33 58 66 1,455 Provision for loan losses 266 — 1 6 (4 ) 269 Total noninterest expense 426 280 25 17 62 810 Income (loss) from continuing operations before income tax expense $ 347 $ (21 ) $ 7 $ 35 $ 8 $ 376 Total assets $ 115,447 $ 7,308 $ 8,902 $ 3,552 $ 29,136 $ 164,345 (a) Net financing revenue and other interest income after the provision for loan losses totaled $936 million and $798 million for the three months ended June 30, 2018 , and 2017, respectively. Six months ended June 30, ($ in millions) Automotive Finance operations Insurance operations Mortgage Finance operations Corporate Finance operations Corporate and Other Consolidated (a) 2018 Net financing revenue and other interest income $ 1,834 $ 25 $ 87 $ 103 $ 94 $ 2,143 Other revenue 129 512 3 22 52 718 Total net revenue 1,963 537 90 125 146 2,861 Provision for loan losses 429 — 2 (6 ) (6 ) 419 Total noninterest expense 884 499 66 44 160 1,653 Income (loss) from continuing operations before income tax expense $ 650 $ 38 $ 22 $ 87 $ (8 ) $ 789 Total assets $ 114,915 $ 7,634 $ 13,385 $ 4,458 $ 30,953 $ 171,345 2017 Net financing revenue and other interest income $ 1,824 $ 29 $ 66 $ 82 $ 45 $ 2,046 Other revenue 208 509 1 28 38 784 Total net revenue 2,032 538 67 110 83 2,830 Provision for loan losses 534 — 2 12 (8 ) 540 Total noninterest expense 863 519 49 38 119 1,588 Income (loss) from continuing operations before income tax expense $ 635 $ 19 $ 16 $ 60 $ (28 ) $ 702 Total assets $ 115,447 $ 7,308 $ 8,902 $ 3,552 $ 29,136 $ 164,345 (a) Net financing revenue and other interest income after the provision for loan losses totaled $1.7 billion and $1.5 billion for the six months ended June 30, 2018 , and 2017, respectively.

Parent and Guarantor Condense54

Parent and Guarantor Condensed Consolidating Financial Statements (Tables)	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Condensed Income Statement [Table Text Block]	Condensed Consolidating Statements of Comprehensive Income Three months ended June 30, 2018 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing revenue and other interest income Interest and fees on finance receivables and loans $ (1 ) $ — $ 1,648 $ — $ 1,647 Interest and fees on finance receivables and loans — intercompany 4 — 1 (5 ) — Interest on loans held-for-sale — — 6 — 6 Interest and dividends on investment securities and other earning assets — — 188 — 188 Interest on cash and cash equivalents 2 — 14 1 17 Interest-bearing cash — intercompany 2 — 2 (4 ) — Operating leases 1 — 373 — 374 Total financing revenue and other interest income 8 — 2,232 (8 ) 2,232 Interest expense Interest on deposits — — 395 4 399 Interest on short-term borrowings 10 — 30 — 40 Interest on long-term debt 257 — 177 — 434 Interest on intercompany debt 4 — 8 (12 ) — Total interest expense 271 — 610 (8 ) 873 Net depreciation expense on operating lease assets 1 — 264 — 265 Net financing (loss) revenue (264 ) — 1,358 — 1,094 Cash dividends from subsidiaries Bank subsidiary 500 500 — (1,000 ) — Nonbank subsidiaries 132 — — (132 ) — Other revenue Insurance premiums and service revenue earned — — 239 — 239 Gain on mortgage and automotive loans, net — — 1 — 1 Other gain on investments, net — — 27 — 27 Other income, net of losses 100 — 185 (188 ) 97 Total other revenue 100 — 452 (188 ) 364 Total net revenue 468 500 1,810 (1,320 ) 1,458 Provision for loan losses 32 — 126 — 158 Noninterest expense Compensation and benefits expense 25 — 267 — 292 Insurance losses and loss adjustment expenses — — 101 — 101 Other operating expenses 173 — 461 (188 ) 446 Total noninterest expense 198 — 829 (188 ) 839 Income from continuing operations before income tax (benefit) expense and undistributed income (loss) of subsidiaries 238 500 855 (1,132 ) 461 Income tax (benefit) expense from continuing operations (66 ) — 179 — 113 Net income from continuing operations 304 500 676 (1,132 ) 348 (Loss) income from discontinued operations, net of tax (1 ) — 2 — 1 Undistributed income (loss) of subsidiaries Bank subsidiary 52 52 — (104 ) — Nonbank subsidiaries (6 ) — — 6 — Net income 349 552 678 (1,230 ) 349 Other comprehensive loss, net of tax (70 ) (56 ) (74 ) 130 (70 ) Comprehensive income $ 279 $ 496 $ 604 $ (1,100 ) $ 279 Three months ended June 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 $ (35 ) $ — $ 1,482 $ — $ 1,447 Interest and fees on finance receivables and loans — intercompany 3 — 2 (5 ) — Interest and dividends on investment securities and other earning assets — — 146 — 146 Interest on cash and cash equivalents 2 — 5 — 7 Interest-bearing cash — intercompany — — 2 (2 ) — Operating leases 3 — 485 — 488 Total financing (loss) revenue and other interest income (27 ) — 2,122 (7 ) 2,088 Interest expense Interest on deposits 1 — 249 — 250 Interest on short-term borrowings 19 — 14 — 33 Interest on long-term debt 274 — 143 — 417 Interest on intercompany debt 4 — 3 (7 ) — Total interest expense 298 — 409 (7 ) 700 Net depreciation expense on operating lease assets 3 — 318 — 321 Net financing (loss) revenue (328 ) — 1,395 — 1,067 Cash dividends from subsidiaries Nonbank subsidiaries 387 — — (387 ) — Other revenue Insurance premiums and service revenue earned — — 227 — 227 Gain on mortgage and automotive loans, net 32 — 4 — 36 Other gain on investments, net — — 23 — 23 Other income, net of losses 163 — 210 (271 ) 102 Total other revenue 195 — 464 (271 ) 388 Total net revenue 254 — 1,859 (658 ) 1,455 Provision for loan losses 82 — 187 — 269 Noninterest expense Compensation and benefits expense 19 — 246 — 265 Insurance losses and loss adjustment expenses — — 125 — 125 Other operating expenses 213 — 478 (271 ) 420 Total noninterest expense 232 — 849 (271 ) 810 (Loss) income from continuing operations before income tax (benefit) expense and undistributed income (loss) of subsidiaries (60 ) — 823 (387 ) 376 Income tax (benefit) expense from continuing operations (93 ) — 215 — 122 Net income from continuing operations 33 — 608 (387 ) 254 Loss from discontinued operations, net of tax — — (2 ) — (2 ) Undistributed income (loss) of subsidiaries Bank subsidiary 375 375 — (750 ) — Nonbank subsidiaries (156 ) — — 156 — Net income 252 375 606 (981 ) 252 Other comprehensive income, net of tax 76 50 72 (122 ) 76 Comprehensive income $ 328 $ 425 $ 678 $ (1,103 ) $ 328 Six months ended June 30, 2018 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Financing revenue and other interest income Interest and fees on finance receivables and loans $ 10 $ — $ 3,180 $ — $ 3,190 Interest and fees on finance receivables and loans — intercompany 6 — 2 (8 ) — Interest on loans held-for-sale — — 6 — 6 Interest and dividends on investment securities and other earning assets — — 365 (1 ) 364 Interest on cash and cash equivalents 4 — 28 — 32 Interest-bearing cash — intercompany 4 — 4 (8 ) — Operating leases 3 — 753 — 756 Total financing revenue and other interest income 27 — 4,338 (17 ) 4,348 Interest expense Interest on deposits — — 750 — 750 Interest on short-term borrowings 20 — 52 — 72 Interest on long-term debt 515 — 330 — 845 Interest on intercompany debt 7 — 10 (17 ) — Total interest expense 542 — 1,142 (17 ) 1,667 Net depreciation expense on operating lease assets 5 — 533 — 538 Net financing (loss) revenue (520 ) — 2,663 — 2,143 Cash dividends from subsidiaries Bank subsidiary 1,500 1,500 — (3,000 ) — Nonbank subsidiaries 301 — — (301 ) — Other revenue Insurance premiums and service revenue earned — — 495 — 495 Gain on mortgage and automotive loans, net 28 — 2 (28 ) 2 Other gain on investments, net — — 15 — 15 Other income, net of losses 196 — 406 (396 ) 206 Total other revenue 224 — 918 (424 ) 718 Total net revenue 1,505 1,500 3,581 (3,725 ) 2,861 Provision for loan losses 113 — 334 (28 ) 419 Noninterest expense Compensation and benefits expense 48 — 550 — 598 Insurance losses and loss adjustment expenses — — 164 — 164 Other operating expenses 355 — 932 (396 ) 891 Total noninterest expense 403 — 1,646 (396 ) 1,653 Income from continuing operations before income tax (benefit) expense and undistributed (loss) income of subsidiaries 989 1,500 1,601 (3,301 ) 789 Income tax (benefit) expense from continuing operations (122 ) — 311 — 189 Net income from continuing operations 1,111 1,500 1,290 (3,301 ) 600 (Loss) income from discontinued operations, net of tax (2 ) — 1 — (1 ) Undistributed (loss) income of subsidiaries Bank subsidiary (545 ) (545 ) — 1,090 — Nonbank subsidiaries 35 — — (35 ) — Net income 599 955 1,291 (2,246 ) 599 Other comprehensive loss, net of tax (398 ) (332 ) (413 ) 745 (398 ) Comprehensive income $ 201 $ 623 $ 878 $ (1,501 ) $ 201 Six months ended June 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 $ (70 ) $ — $ 2,885 $ — $ 2,815 Interest and fees on finance receivables and loans — intercompany 7 — 4 (11 ) — Interest and dividends on investment securities and other earning assets — — 281 (1 ) 280 Interest on cash and cash equivalents 4 — 8 — 12 Interest-bearing cash — intercompany — — 3 (3 ) — Operating leases 6 — 1,025 — 1,031 Total financing (loss) revenue and other interest income (53 ) — 4,206 (15 ) 4,138 Interest expense Interest on deposits 2 — 479 — 481 Interest on short-term borrowings 36 — 24 — 60 Interest on long-term debt 556 — 285 — 841 Interest on intercompany debt 8 — 7 (15 ) — Total interest expense 602 — 795 (15 ) 1,382 Net depreciation expense on operating lease assets 5 — 705 — 710 Net financing (loss) revenue (660 ) — 2,706 — 2,046 Cash dividends from subsidiaries Nonbank subsidiaries 427 — — (427 ) — Other revenue Insurance premiums and service revenue earned — — 468 — 468 Gain on mortgage and automotive loans, net 30 — 20 — 50 Other gain on investments, net — — 50 — 50 Other income, net of losses 431 — 433 (648 ) 216 Total other revenue 461 — 971 (648 ) 784 Total net revenue 228 — 3,677 (1,075 ) 2,830 Provision for loan losses 189 — 351 — 540 Noninterest expense Compensation and benefits expense 140 — 410 — 550 Insurance losses and loss adjustment expenses — — 213 — 213 Other operating expenses 501 — 972 (648 ) 825 Total noninterest expense 641 — 1,595 (648 ) 1,588 (Loss) income from continuing operations before income tax (benefit) expense and undistributed income of subsidiaries (602 ) — 1,731 (427 ) 702 Income tax (benefit) expense from continuing operations (227 ) — 462 — 235 Net (loss) income from continuing operations (375 ) — 1,269 (427 ) 467 Income (loss) from discontinued operations, net of tax 2 — (3 ) — (1 ) Undistributed income of subsidiaries Bank subsidiary 764 764 — (1,528 ) — Nonbank subsidiaries 75 — — (75 ) — Net income 466 764 1,266 (2,030 ) 466 Other comprehensive income, net of tax 96 55 91 (146 ) 96 Comprehensive income $ 562 $ 819 $ 1,357 $ (2,176 ) $ 562
Condensed Balance Sheet [Table Text Block]	Condensed Consolidating Balance Sheet June 30, 2018 ($ in millions) Parent (a) Guarantors Nonguarantors (a) Consolidating adjustments Ally consolidated Assets Cash and cash equivalents Noninterest-bearing $ 49 $ — $ 750 $ — $ 799 Interest-bearing 6 — 3,119 — 3,125 Interest-bearing — intercompany 1,016 — 569 (1,585 ) — Total cash and cash equivalents 1,071 — 4,438 (1,585 ) 3,924 Equity securities — — 521 — 521 Available-for-sale securities — — 23,296 — 23,296 Held-to-maturity securities — — 2,146 (57 ) 2,089 Loans held-for-sale, net — — 328 — 328 Finance receivables and loans, net Finance receivables and loans, net 5,647 — 119,897 — 125,544 Intercompany loans to Nonbank subsidiaries 786 — 405 (1,191 ) — Allowance for loan losses (128 ) — (1,129 ) — (1,257 ) Total finance receivables and loans, net 6,305 — 119,173 (1,191 ) 124,287 Investment in operating leases, net 10 — 8,629 — 8,639 Intercompany receivables from Bank subsidiary 106 — — (106 ) — Nonbank subsidiaries 61 — 88 (149 ) — Investment in subsidiaries Bank subsidiary 16,163 16,163 — (32,326 ) — Nonbank subsidiaries 7,162 — — (7,162 ) — Premiums receivable and other insurance assets — — 2,247 — 2,247 Other assets 2,123 — 5,129 (1,238 ) 6,014 Total assets $ 33,001 $ 16,163 $ 165,995 $ (43,814 ) $ 171,345 Liabilities Deposit liabilities Noninterest-bearing $ — $ — $ 153 $ — $ 153 Interest-bearing 6 — 98,575 — 98,581 Interest-bearing — intercompany — — 1,016 (1,016 ) — Total deposit liabilities 6 — 99,744 (1,016 ) 98,734 Short-term borrowings 2,666 — 4,442 — 7,108 Long-term debt 15,571 — 31,757 — 47,328 Intercompany debt to Bank subsidiary 57 — — (57 ) — Nonbank subsidiaries 973 — 786 (1,759 ) — Intercompany payables to Nonbank subsidiaries 130 — 129 (259 ) — Interest payable 192 — 376 — 568 Unearned insurance premiums and service revenue — — 2,957 — 2,957 Accrued expenses and other liabilities 267 — 2,479 (1,235 ) 1,511 Total liabilities 19,862 — 142,670 (4,326 ) 158,206 Total equity 13,139 16,163 23,325 (39,488 ) 13,139 Total liabilities and equity $ 33,001 $ 16,163 $ 165,995 $ (43,814 ) $ 171,345 (a) Amounts presented are based upon the legal transfer of the underlying assets to VIEs in order to reflect legal ownership. December 31, 2017 ($ in millions) Parent (a) Guarantors Nonguarantors (a) Consolidating adjustments Ally consolidated Assets Cash and cash equivalents Noninterest-bearing $ 74 $ — $ 770 $ — $ 844 Interest-bearing 5 — 3,403 — 3,408 Interest-bearing — intercompany 1,138 — 695 (1,833 ) — Total cash and cash equivalents 1,217 — 4,868 (1,833 ) 4,252 Equity securities — — 518 — 518 Available-for-sale securities — — 22,303 — 22,303 Held-to-maturity securities — — 1,973 (74 ) 1,899 Loans held-for-sale, net — — 108 — 108 Finance receivables and loans, net Finance receivables and loans, net 7,434 — 115,459 — 122,893 Intercompany loans to Nonbank subsidiaries 879 — 408 (1,287 ) — Allowance for loan losses (185 ) — (1,091 ) — (1,276 ) Total finance receivables and loans, net 8,128 — 114,776 (1,287 ) 121,617 Investment in operating leases, net 19 — 8,722 — 8,741 Intercompany receivables from Bank subsidiary 80 — — (80 ) — Nonbank subsidiaries 71 — 77 (148 ) — Investment in subsidiaries Bank subsidiary 16,962 16,962 — (33,924 ) — Nonbank subsidiaries 8,111 — — (8,111 ) — Premiums receivable and other insurance assets — — 2,082 (35 ) 2,047 Other assets 2,207 — 5,105 (1,649 ) 5,663 Total assets $ 36,795 $ 16,962 $ 160,532 $ (47,141 ) $ 167,148 Liabilities Deposit liabilities Noninterest-bearing $ — $ — $ 108 $ — $ 108 Interest-bearing 12 — 93,136 — 93,148 Interest-bearing — intercompany — — 1,139 (1,139 ) — Total deposit liabilities 12 — 94,383 (1,139 ) 93,256 Short-term borrowings 3,171 — 8,242 — 11,413 Long-term debt 17,966 — 26,260 — 44,226 Intercompany debt to Bank subsidiary 74 — — (74 ) — Nonbank subsidiaries 1,103 — 879 (1,982 ) — Intercompany payables to Bank subsidiary 4 — — (4 ) — Nonbank subsidiaries 132 — 127 (259 ) — Interest payable 200 — 175 — 375 Unearned insurance premiums and service revenue — — 2,604 — 2,604 Accrued expenses and other liabilities 639 — 2,790 (1,649 ) 1,780 Total liabilities 23,301 — 135,460 (5,107 ) 153,654 Total equity 13,494 16,962 25,072 (42,034 ) 13,494 Total liabilities and equity $ 36,795 $ 16,962 $ 160,532 $ (47,141 ) $ 167,148 (a) Amounts presented are based upon the legal transfer of the underlying assets to VIEs in order to reflect legal ownership.
Parent Guarantor Consolidating Statement of Cash Flows [Table Text Block]	Condensed Consolidating Statement of Cash Flows Six months ended June 30, 2018 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Operating activities Net cash provided by operating activities $ 958 $ 1,500 $ 2,853 $ (3,302 ) $ 2,009 Investing activities Purchases of equity securities — — (500 ) — (500 ) Proceeds from sales of equity securities — — 535 — 535 Purchases of available-for-sale securities — — (4,094 ) — (4,094 ) Proceeds from sales of available-for-sale securities — — 390 — 390 Proceeds from repayments of available-for-sale securities — — 1,621 — 1,621 Purchases of held-to-maturity securities — — (316 ) — (316 ) Proceeds from repayments of held-to-maturity securities — — 72 — 72 Net change in investment securities — intercompany — — 17 (17 ) — Purchases of finance receivables and loans held-for-investment — — (3,431 ) 820 (2,611 ) Proceeds from sales of finance receivables and loans initially held-for-investment 820 — — (820 ) — Originations and repayments of finance receivables and loans held-for-investment and other, net 1,331 — (1,969 ) — (638 ) Net change in loans — intercompany 83 — (5 ) (78 ) — Purchases of operating lease assets — — (2,107 ) — (2,107 ) Disposals of operating lease assets 6 — 1,757 — 1,763 Capital contributions to subsidiaries (57 ) (6 ) — 63 — Returns of contributed capital 194 — — (194 ) — Net change in nonmarketable equity investments — — (46 ) — (46 ) Other, net (3 ) — (183 ) — (186 ) Net cash provided by (used in) investing activities 2,374 (6 ) (8,259 ) (226 ) (6,117 ) Financing activities Net change in short-term borrowings — third party (505 ) — (3,800 ) — (4,305 ) Net (decrease) increase in deposits (6 ) — 5,324 123 5,441 Proceeds from issuance of long-term debt — third party 32 — 12,908 — 12,940 Repayments of long-term debt — third party (2,412 ) — (7,388 ) — (9,800 ) Net change in debt — intercompany (138 ) — (83 ) 221 — Repurchase of common stock (380 ) — — — (380 ) Dividends paid — third party (115 ) — — — (115 ) Dividends paid and returns of contributed capital — intercompany — (1,500 ) (1,995 ) 3,495 — Capital contributions from parent — 6 57 (63 ) — Net cash (used in) provided by financing activities (3,524 ) (1,494 ) 5,023 3,776 3,781 Effect of exchange-rate changes on cash and cash equivalents — — (3 ) — (3 ) Net decrease in cash and cash equivalents and restricted cash (192 ) — (386 ) 248 (330 ) Cash and cash equivalents and restricted cash at beginning of year 1,395 — 5,707 (1,833 ) 5,269 Cash and cash equivalents and restricted cash at June 30, $ 1,203 $ — $ 5,321 $ (1,585 ) $ 4,939 The following table provides a reconciliation of cash and cash equivalents and restricted cash from the Condensed Consolidated Balance Sheet to the Condensed Consolidated Statement of Cash Flows. June 30, 2018 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet $ 1,071 $ — $ 4,438 $ (1,585 ) $ 3,924 Restricted cash included in other assets on the Condensed Consolidated Balance Sheet (a) 132 — 883 — 1,015 Total cash and cash equivalents and restricted cash as disclosed in the Condensed Consolidated Statement of Cash Flows $ 1,203 $ — $ 5,321 $ (1,585 ) $ 4,939 (a) Restricted cash balances relate primarily to Ally securitization arrangements. Refer to Note 11 for additional details describing the nature of restricted cash balances. Six months ended June 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Operating activities Net cash provided by operating activities $ 561 $ — $ 1,856 $ (347 ) $ 2,070 Investing activities Purchases of equity securities — — (363 ) — (363 ) Proceeds from sales of equity securities — — 484 — 484 Purchases of available-for-sale securities — — (5,490 ) — (5,490 ) Proceeds from sales of available-for-sale securities — — 1,678 — 1,678 Proceeds from repayments of available-for-sale securities — — 1,230 — 1,230 Purchases of held-to-maturity securities — — (313 ) — (313 ) Proceeds from repayments of held-to-maturity securities — — 17 — 17 Net change in investment securities — intercompany 1 — 269 (270 ) — Purchases of finance receivables and loans held-for-investment (35 ) — (1,782 ) — (1,817 ) Proceeds from sales of finance receivables and loans initially held-for-investment 67 — 1,213 — 1,280 Originations and repayments of finance receivables and loans held-for-investment and other, net 1,044 — (676 ) (1,956 ) (1,588 ) Net change in loans — intercompany 1,864 — 246 (2,110 ) — Purchases of operating lease assets — — (1,965 ) — (1,965 ) Disposals of operating lease assets 4 — 3,039 — 3,043 Capital contributions to subsidiaries (824 ) — — 824 — Returns of contributed capital 838 — — (838 ) — Net change in nonmarketable equity investments — — 107 — 107 Other, net (21 ) — 27 (96 ) (90 ) Net cash provided by (used in) investing activities 2,938 — (2,279 ) (4,446 ) (3,787 ) Financing activities Net change in short-term borrowings — third party 1,083 — (3,045 ) — (1,962 ) Net (decrease) increase in deposits (123 ) — 7,256 — 7,133 Proceeds from issuance of long-term debt — third party 353 — 7,016 1,961 9,330 Repayments of long-term debt — third party (3,323 ) — (11,043 ) — (14,366 ) Net change in debt — intercompany (370 ) — (1,864 ) 2,234 — Repurchase of common stock (373 ) — — — (373 ) Dividends paid — third party (75 ) — — — (75 ) Dividends paid and returns of contributed capital — intercompany — — (1,266 ) 1,266 — Capital contributions from parent — — 824 (824 ) — Net cash used in financing activities (2,828 ) — (2,122 ) 4,637 (313 ) Effect of exchange-rate changes on cash and cash equivalents — — 2 — 2 Net increase (decrease) in cash and cash equivalents and restricted cash 671 — (2,543 ) (156 ) (2,028 ) Cash and cash equivalents and restricted cash at beginning of year 989 — 7,293 (401 ) 7,881 Cash and cash equivalents and restricted cash at June 30, $ 1,660 $ — $ 4,750 $ (557 ) $ 5,853 The following table provides a reconciliation of cash and cash equivalents and restricted cash from the Condensed Consolidated Balance Sheet to the Condensed Consolidated Statement of Cash Flows. June 30, 2017 ($ in millions) Parent Guarantors Nonguarantors Consolidating adjustments Ally consolidated Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet $ 1,441 $ — $ 3,493 $ (557 ) $ 4,377 Restricted cash included in other assets on the Condensed Consolidated Balance Sheet (a) 219 — 1,257 — 1,476 Total cash and cash equivalents and restricted cash as disclosed in the Condensed Consolidated Statement of Cash Flows $ 1,660 $ — $ 4,750 $ (557 ) $ 5,853 (a) Restricted cash balances relate primarily to Ally securitization arrangements. Refer to Note 11 for additional details describing the nature of restricted cash balances.

Description of Business, Basi55

Description of Business, Basis of Presentation, and Changes in Significant Accounting Policies (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jan. 01, 2018
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 126	$ 126
Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	20	(7)
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (42)	$ 0

Revenue from Contracts with C56

Revenue from Contracts with Customers (Contract with Customer, Asset and Liability) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Premiums receivable and other insurance assets	$ 2,247		$ 2,047
Other Assets	6,014		5,663
Assets	171,345		167,148	$ 164,345
Unearned Premiums	2,957		2,604
Liabilities	158,206		153,654
Retained Earnings (Accumulated Deficit)	(6,026)		(6,406)
Stockholders' Equity Attributable to Parent	13,139	$ 13,375	13,494	$ 13,473	$ 13,317
Liabilities and Equity	$ 171,345		$ 167,148
Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Premiums receivable and other insurance assets		122
Other Assets		41
Assets		163
Unearned Premiums		289
Liabilities		289
Retained Earnings (Accumulated Deficit)		(126)
Stockholders' Equity Attributable to Parent		(126)
Liabilities and Equity		163
Day One Balance [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Premiums receivable and other insurance assets		2,169
Other Assets		5,704
Assets		167,311
Unearned Premiums		2,893
Liabilities		153,943
Retained Earnings (Accumulated Deficit)		(6,532)
Stockholders' Equity Attributable to Parent		13,368
Liabilities and Equity		$ 167,311

Revenue from Contracts with C57

Revenue from Contracts with Customers (Impact of ASU 2014-09 on Balance Sheet and Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Insurance Services Revenue	$ 239	$ 227	$ 495	$ 468
Nonoperating Income (Expense)	364	388	718	784
Revenues	1,458	1,455	2,861	2,830
Labor and Related Expense	292	265	598	550
Other Noninterest Expense	446	420	891	825
Noninterest Expense	839	810	1,653	1,588
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	461	376	789	702
Income Tax Expense (Benefit)	113	122	189	235
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	348	254	600	467
Net Income (Loss) Attributable to Parent	349	252	599	466
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	279	328	201	562
Premiums receivable and other insurance assets	2,247		2,247			$ 2,047
Other Assets	6,014		6,014			5,663
Assets	171,345	164,345	171,345	164,345		167,148
Unearned Premiums	2,957		2,957			2,604
Liabilities	158,206		158,206			153,654
Retained Earnings (Accumulated Deficit)	(6,026)		(6,026)			(6,406)
Stockholders' Equity Attributable to Parent	13,139	13,473	13,139	13,473	$ 13,375	13,494	$ 13,317
Liabilities and Equity	171,345		171,345			167,148
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Insurance Services Revenue	(9)		(15)
Nonoperating Income (Expense)	(9)		(15)
Revenues	(9)		(15)
Labor and Related Expense	(1)		(2)
Other Noninterest Expense	(3)		(5)
Noninterest Expense	(4)		(7)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(5)		(8)
Income Tax Expense (Benefit)	(1)		(2)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(4)		(6)
Net Income (Loss) Attributable to Parent	(4)		(6)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(4)		(6)
Premiums receivable and other insurance assets	128		128
Other Assets	43		43
Assets	171		171
Unearned Premiums	304		304
Liabilities	304		304
Retained Earnings (Accumulated Deficit)	(133)		(133)
Stockholders' Equity Attributable to Parent	(133)		(133)
Liabilities and Equity	171		171
Retained Earnings [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net Income (Loss) Attributable to Parent	349	252	599	466
Stockholders' Equity Attributable to Parent	$ (6,026)	$ (6,760)	$ (6,026)	$ (6,760)	$ (6,510)	$ (6,406)	$ (7,151)

Revenue from Contracts with C58

Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Insurance Commissions	$ 109	$ 104	$ 219	$ 203
Revenue from Contract with Customer, Excluding Assessed Tax	172		344
Revenue Outside of Scope of the Amendments to the Revenue Recognition Principles	192		374
Nonoperating Income (Expense)	364	388	718	784
Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Liability	289		289
Deferred Revenue, Revenue Recognized	22		44
Revenue, Remaining Performance Obligation	2,600		2,600
Deferred Sales Commission	1,500		1,500
Insurance Commissions	106		209
Revenue from Contract with Customer, Excluding Assessed Tax	125		248
Remarketing Activities [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	21		44
Brokerage Commissions and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	15		31
Brokered/Agent Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4		8
Deposits and Banking [Member]
Disaggregation of Revenue [Line Items]
Fees and Commissions, Debit Cards	3		6
Expense, Debt Cards	2		5
Revenue from Contract with Customer, Excluding Assessed Tax	3		6
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4		7
Automotive Finance Operations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	25		50
Revenue Outside of Scope of the Amendments to the Revenue Recognition Principles	38		79
Nonoperating Income (Expense)	63	107	129	208
Automotive Finance Operations [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Automotive Finance Operations [Member] | Remarketing Activities [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	21		44
Automotive Finance Operations [Member] | Brokerage Commissions and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Automotive Finance Operations [Member] | Brokered/Agent Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Automotive Finance Operations [Member] | Deposits and Banking [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Automotive Finance Operations [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4		6
Automotive Finance Operations [Member] | Sale of Off-lease Vehicles [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	16		34
Insurance Operations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	129		257
Revenue Outside of Scope of the Amendments to the Revenue Recognition Principles	137		255
Insurance Operations [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	125		248
Insurance Operations [Member] | Remarketing Activities [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Insurance Operations [Member] | Brokerage Commissions and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Insurance Operations [Member] | Brokered/Agent Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4		8
Insurance Operations [Member] | Deposits and Banking [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Insurance Operations [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		1
Mortgage Finance [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Revenue Outside of Scope of the Amendments to the Revenue Recognition Principles	2		3
Nonoperating Income (Expense)	2	1	3	1
Mortgage Finance [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Mortgage Finance [Member] | Remarketing Activities [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Mortgage Finance [Member] | Brokerage Commissions and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Mortgage Finance [Member] | Brokered/Agent Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Mortgage Finance [Member] | Deposits and Banking [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Mortgage Finance [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate Finance Operations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Revenue Outside of Scope of the Amendments to the Revenue Recognition Principles	14		22
Nonoperating Income (Expense)	14	10	22	28
Corporate Finance Operations [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate Finance Operations [Member] | Remarketing Activities [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate Finance Operations [Member] | Brokerage Commissions and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate Finance Operations [Member] | Brokered/Agent Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate Finance Operations [Member] | Deposits and Banking [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate Finance Operations [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	18		37
Revenue Outside of Scope of the Amendments to the Revenue Recognition Principles	1		15
Nonoperating Income (Expense)	19	$ 25	52	$ 38
Corporate and Other [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate and Other [Member] | Remarketing Activities [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate and Other [Member] | Brokerage Commissions and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	15		31
Corporate and Other [Member] | Brokered/Agent Commissions [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Corporate and Other [Member] | Deposits and Banking [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3		6
Corporate and Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0		0
Remainder of 2018 [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue, Remaining Performance Obligation	407		407
2019 [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue, Remaining Performance Obligation	663		663
2020 [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue, Remaining Performance Obligation	564		564
2021 [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue, Remaining Performance Obligation	423		423
2022 and Thereafter [Member] | Noninsurance Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue, Remaining Performance Obligation	$ 501		$ 501

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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Nonoperating Income (Expense) [Abstract]
Fees and Commissions, Other	$ 25	$ 25	$ 54	$ 52
Remarketing Fees	21	27	44	56
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	8	14	16	30
Income (Loss) from Equity Method Investments	7	5	13	5
Other Income	36	31	79	73
Noninterest Income, Other Operating Income	$ 97	$ 102	$ 206	$ 216

Reserves for Insurance Losses60

Reserves for Insurance Losses and Loss Adjustment Expenses Reserves for Insurance Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense			$ 140	$ 149
Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments			108	108
Liability for Unpaid Claims and Claims Adjustment Expense, Net			32	41
Current Year Claims and Claims Adjustment Expense			159	211
Prior Year Claims and Claims Adjustment Expense			5	2
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	$ 101	$ 125	164	213
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year			121	183
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years			26	27
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid			147	210
Liability for Unpaid Claims and Claims Adjustment Expense, Net	49	44	49	44
Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments	100	135	100	135
Liability for Claims and Claims Adjustment Expense	$ 149	$ 179	$ 149	$ 179

Other Operating Expenses (Sched

Other Operating Expenses (Schedule Of Other Operating Expenses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Operating Expenses [Abstract]
Insurance Commissions	$ 109	$ 104	$ 219	$ 203
Communications and Information Technology	74	71	145	140
Lease And Loan Administration	40	39	82	75
Marketing and Advertising Expense	29	33	68	63
Professional Fees	35	27	67	53
Federal Deposit Insurance Corporation Premium Expense	35	28	65	55
Vehicle remarketing and repossession	26	25	58	53
Depreciation, Nonproduction	22	23	42	45
Occupancy, Net	11	11	22	23
Taxes, Miscellaneous	6	8	14	16
Amortization of Intangible Assets	3	3	6	6
Other Cost and Expense, Operating	56	48	103	93
Other Noninterest Expense	$ 446	$ 420	$ 891	$ 825

Investment Securities (Investme

Investment Securities (Investment Table) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Held-to-maturity securities	$ 2,089	$ 1,899
Held-to-maturity Securities, Fair Value	2,007	1,865
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	1,200	1,000
US Treasury and Government [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,963	1,831
Available-for-sale Debt Securities Gross Unrealized Gain	1	0
Available-for-sale Debt Securities, Gross Unrealized Loss	(90)	(54)
Available-for-sale Securities, Debt Securities	1,874	1,777
US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	865	850
Available-for-sale Debt Securities Gross Unrealized Gain	5	11
Available-for-sale Debt Securities, Gross Unrealized Loss	(19)	(7)
Available-for-sale Securities, Debt Securities	851	854
Foreign Government Debt Securities [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	155	153
Available-for-sale Debt Securities Gross Unrealized Gain	1	2
Available-for-sale Debt Securities, Gross Unrealized Loss	(2)	(1)
Available-for-sale Securities, Debt Securities	154	154
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	15,559	14,412
Available-for-sale Debt Securities Gross Unrealized Gain	4	35
Available-for-sale Debt Securities, Gross Unrealized Loss	(497)	(156)
Available-for-sale Securities, Debt Securities	15,066	14,291
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity securities	2,062	1,863
Held-to-maturity Securities, Unrecognized Holding Gain	1	3
Held-to-maturity Securities, Unrecognized Holding Loss	(83)	(37)
Held-to-maturity Securities, Fair Value	1,980	1,829
Residential Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,716	2,517
Available-for-sale Debt Securities Gross Unrealized Gain	2	11
Available-for-sale Debt Securities, Gross Unrealized Loss	(93)	(34)
Available-for-sale Securities, Debt Securities	2,625	2,494
Commercial Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	644	541
Available-for-sale Debt Securities Gross Unrealized Gain	1	1
Available-for-sale Debt Securities, Gross Unrealized Loss	(3)	(1)
Available-for-sale Securities, Debt Securities	642	541
Asset-backed Securities [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	870	933
Available-for-sale Debt Securities Gross Unrealized Gain	2	4
Available-for-sale Debt Securities, Gross Unrealized Loss	(4)	(1)
Available-for-sale Securities, Debt Securities	868	936
Asset-backed Securities [Member] | Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity securities	27	36
Held-to-maturity Securities, Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Unrecognized Holding Loss	0	0
Held-to-maturity Securities, Fair Value	27	36
Corporate Debt Securities [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,258	1,262
Available-for-sale Debt Securities Gross Unrealized Gain	1	5
Available-for-sale Debt Securities, Gross Unrealized Loss	(43)	(11)
Available-for-sale Securities, Debt Securities	1,216	1,256
Debt Securities [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	24,030	22,499
Available-for-sale Debt Securities Gross Unrealized Gain	17	69
Available-for-sale Debt Securities, Gross Unrealized Loss	(751)	(265)
Available-for-sale Securities, Debt Securities	23,296	22,303
Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity securities	2,089	1,899
Held-to-maturity Securities, Unrecognized Holding Gain	1	3
Held-to-maturity Securities, Unrecognized Holding Loss	(83)	(37)
Held-to-maturity Securities, Fair Value	2,007	1,865
Federal Home Loan Bank Certificates and Obligations (FHLB) [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Pledged Assets Separately Reported, Securities Pledged for Federal Home Loan Bank, at Fair Value	7,100	7,800
Federal Home Loan Bank Certificates and Obligations (FHLB) [Member] | Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Pledged Assets Separately Reported, Securities Pledged for Federal Home Loan Bank, at Fair Value	962	664
Insurance Operations [Member]
Schedule of Investments [Line Items]
Deposit Assets	$ 12	$ 12

Investment Securities (Invest63

Investment Securities (Investments Classified by Contractual Maturity Date) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Cash Equivalents, at Carrying Value	$ 54	$ 10
Held-to-maturity Securities [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	$ 2,089	$ 1,899
Held-to-Maturity Debt Securities, Yield	3.10%	3.10%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 0	$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield	0.00%	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 26	$ 35
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield	1.80%	1.70%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 1	$ 1
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield	3.00%	3.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 2,062	$ 1,863
Held-to-Maturity Securities, Due After Ten Years, Yield	3.10%	3.10%
Available-for-sale Securities [Member] | US Treasury and Government [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 1,874	$ 1,777
Available-for-sale debt securities, Yield	1.90%	1.70%
Available-for-sale debt securities, Due in one year or less, Amount	$ 13	$ 0
Available-for-sale debt securities, Due in one year or less, Yield	1.40%	0.00%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 578	$ 487
Available-for-sale debt securities, Due after one year through five years, Yield	1.90%	1.70%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 1,283	$ 1,290
Available-for-sale debt securities, Due after five years through ten years, Yield	1.80%	1.80%
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	$ 1,963	$ 1,831
Available-for-sale Securities [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 851	$ 854
Available-for-sale debt securities, Yield	3.10%	2.90%
Available-for-sale debt securities, Due in one year or less, Amount	$ 35	$ 76
Available-for-sale debt securities, Due in one year or less, Yield	3.40%	1.80%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 53	$ 36
Available-for-sale debt securities, Due after one year through five years, Yield	2.20%	2.30%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 237	$ 203
Available-for-sale debt securities, Due after five years through ten years, Yield	2.60%	2.50%
Available-for-sale debt securities, Due after ten years, Amount	$ 526	$ 539
Available-for-sale debt securities, Due after ten years, Yield	3.40%	3.30%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 865	$ 850
Available-for-sale Securities [Member] | Foreign Government Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 154	$ 154
Available-for-sale debt securities, Yield	2.50%	2.50%
Available-for-sale debt securities, Due in one year or less, Amount	$ 25	$ 0
Available-for-sale debt securities, Due in one year or less, Yield	3.30%	0.00%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 61	$ 80
Available-for-sale debt securities, Due after one year through five years, Yield	2.30%	2.50%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 68	$ 74
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	$ 155	$ 153
Available-for-sale Securities [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 15,066	$ 14,291
Available-for-sale debt securities, Yield	3.20%	3.10%
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	$ 25	$ 3
Available-for-sale debt securities, Due after five years through ten years, Yield	2.00%	2.90%
Available-for-sale debt securities, Due after ten years, Amount	$ 15,041	$ 14,288
Available-for-sale debt securities, Due after ten years, Yield	3.20%	3.10%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 15,559	$ 14,412
Available-for-sale Securities [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 2,625	$ 2,494
Available-for-sale debt securities, Yield	3.20%	3.10%
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	$ 2,625	$ 2,494
Available-for-sale debt securities, Due after ten years, Yield	3.20%	3.10%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 2,716	$ 2,517
Available-for-sale Securities [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 642	$ 541
Available-for-sale debt securities, Yield	3.60%	3.20%
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	$ 30
Available-for-sale debt securities, Due after one year through five years, Yield	0.00%	3.10%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 31	$ 31
Available-for-sale debt securities, Due after five years through ten years, Yield	3.60%	3.10%
Available-for-sale debt securities, Due after ten years, Amount	$ 611	$ 480
Available-for-sale debt securities, Due after ten years, Yield	3.60%	3.20%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 644	$ 541
Available-for-sale Securities [Member] | Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 868	$ 936
Available-for-sale debt securities, Yield	3.30%	3.10%
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	$ 618	$ 698
Available-for-sale debt securities, Due after one year through five years, Yield	3.30%	3.10%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 137	$ 106
Available-for-sale debt securities, Due after five years through ten years, Yield	3.60%	3.10%
Available-for-sale debt securities, Due after ten years, Amount	$ 113	$ 132
Available-for-sale debt securities, Due after ten years, Yield	3.00%	2.80%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 870	$ 933
Available-for-sale Securities [Member] | Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 1,216	$ 1,256
Available-for-sale debt securities, Yield	3.10%	2.90%
Available-for-sale debt securities, Due in one year or less, Amount	$ 122	$ 140
Available-for-sale debt securities, Due in one year or less, Yield	2.80%	2.60%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 472	$ 513
Available-for-sale debt securities, Due after one year through five years, Yield	2.70%	2.60%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 589	$ 564
Available-for-sale debt securities, Due after five years through ten years, Yield	3.30%	3.20%
Available-for-sale debt securities, Due after ten years, Amount	$ 33	$ 39
Available-for-sale debt securities, Due after ten years, Yield	4.90%	4.70%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 1,258	$ 1,262
Available-for-sale Securities [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Securities	$ 23,296	$ 22,303
Available-for-sale debt securities, Yield	3.10%	3.00%
Available-for-sale debt securities, Due in one year or less, Amount	$ 195	$ 216
Available-for-sale debt securities, Due in one year or less, Yield	2.90%	2.30%
Available-for-sale debt securities, Due after one year through five years, Amount	$ 1,782	$ 1,844
Available-for-sale debt securities, Due after one year through five years, Yield	2.60%	2.50%
Available-for-sale debt securities, Due after five years through ten years, Amount	$ 2,370	$ 2,271
Available-for-sale debt securities, Due after five years through ten years, Yield	2.40%	2.30%
Available-for-sale debt securities, Due after ten years, Amount	$ 18,949	$ 17,972
Available-for-sale debt securities, Due after ten years, Yield	3.20%	3.10%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 24,030	$ 22,499
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	195	217
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	1,811	1,852
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	2,476	2,314
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	19,548	18,116
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	$ 2,062	$ 1,863
Held-to-Maturity Debt Securities, Yield	3.10%	3.10%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 0	$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield	0.00%	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 0	$ 0
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield	0.00%	0.00%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 0	$ 0
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield	0.00%	0.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 2,062	$ 1,863
Held-to-Maturity Securities, Due After Ten Years, Yield	3.10%	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	$ 27	$ 36
Held-to-Maturity Debt Securities, Yield	1.80%	1.70%
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 0	$ 0
Held-to-Maturity Debt Securities, Due in One Year or Less, Yield	0.00%	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 26	$ 35
Held-to-Maturity Debt Securities, Due After One Year Through Five Years, Yield	1.80%	1.70%
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	$ 1	$ 1
Held-to-Maturity Debt Securities, Due After Five Years Through Ten Years, Yield	3.00%	3.00%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 0	$ 0
Held-to-Maturity Securities, Due After Ten Years, Yield	0.00%	0.00%

Investment Securities (Invest64

Investment Securities (Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Taxable interest	$ 164	$ 130	$ 318	$ 249
Taxable dividends	3	3	6	5
Interest and dividends exempt from U.S. federal income tax	6	6	12	11
Interest and Dividend Income, Securities, Operating, Available-for-sale	188	146	364	280
Excludes Other Earning Assets [Member]
Interest and Dividend Income, Securities, Operating, Available-for-sale	$ 173	$ 139	$ 336	$ 265

Investment Securities (Schedule

Investment Securities (Schedule Of Realized Gain (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Available-for-sale Securities [Abstract]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	$ 0	$ 0	$ 0	$ 0
Available-for-sale Securities, Gross Realized Gains	1	24	7	51
Available-for-sale Securities, Gross Realized Losses	0	(1)	0	(1)
Available-for-sale Securities, Gross Realized Gain (Loss)	1	23	7	50
Net realized gain (loss) on equity securities	18		40
Available-for-sale Equity Securities, Gross Unrealized Gain	(8)		32
Gain (Loss) on Investments	$ 27	$ 23	$ 15	$ 50

Investment Securities (Schedu66

Investment Securities (Schedule of Unrealized Loss on Investments) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	$ 485	$ 471
Available-for-sale Securities, Unrealized Loss Less than 12 months	(19)	(8)
Available-for-sale Securities, Fair value 12 months or longer	1,275	1,305
Available-for-sale Securities, Unrealized Loss 12 months or longer	(71)	(46)
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	420	242
Available-for-sale Securities, Unrealized Loss Less than 12 months	(8)	(2)
Available-for-sale Securities, Fair value 12 months or longer	181	183
Available-for-sale Securities, Unrealized Loss 12 months or longer	(11)	(5)
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	56	80
Available-for-sale Securities, Unrealized Loss Less than 12 months	(1)	(1)
Available-for-sale Securities, Fair value 12 months or longer	25	4
Available-for-sale Securities, Unrealized Loss 12 months or longer	(1)	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	8,834	4,066
Available-for-sale Securities, Unrealized Loss Less than 12 months	(215)	(19)
Available-for-sale Securities, Fair value 12 months or longer	5,331	5,671
Available-for-sale Securities, Unrealized Loss 12 months or longer	(282)	(137)
Held-to-maturity Securities, Fair Value, Less than 12 months	1,152	773
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	33	5
Held-to-maturity Securities, Fair value Less 12 months or longer	668	687
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	50	32
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	1,642	857
Available-for-sale Securities, Unrealized Loss Less than 12 months	(35)	(2)
Available-for-sale Securities, Fair value 12 months or longer	688	773
Available-for-sale Securities, Unrealized Loss 12 months or longer	(58)	(32)
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	91	76
Available-for-sale Securities, Unrealized Loss Less than 12 months	(2)	(1)
Available-for-sale Securities, Fair value 12 months or longer	18	21
Available-for-sale Securities, Unrealized Loss 12 months or longer	(1)	0
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	479	220
Available-for-sale Securities, Unrealized Loss Less than 12 months	(3)	(1)
Available-for-sale Securities, Fair value 12 months or longer	71	91
Available-for-sale Securities, Unrealized Loss 12 months or longer	(1)	0
Held-to-maturity Securities, Fair Value, Less than 12 months	24	35
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	0	0
Held-to-maturity Securities, Fair value Less 12 months or longer	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0	0
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	885	529
Available-for-sale Securities, Unrealized Loss Less than 12 months	(26)	(4)
Available-for-sale Securities, Fair value 12 months or longer	254	194
Available-for-sale Securities, Unrealized Loss 12 months or longer	(17)	(7)
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	12,892	6,541
Available-for-sale Securities, Unrealized Loss Less than 12 months	(309)	(38)
Available-for-sale Securities, Fair value 12 months or longer	7,843	8,242
Available-for-sale Securities, Unrealized Loss 12 months or longer	(442)	(227)
Held-to-maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Fair Value, Less than 12 months	1,176	808
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	33	5
Held-to-maturity Securities, Fair value Less 12 months or longer	668	687
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	$ 50	$ 32

Finance Receivables and Loans67

Finance Receivables and Loans, Net (Schedule of Accounts, Notes, Loans and Financing Receivables) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 125,544	$ 122,893	$ 120,528
Loans and Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	612	551
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	85,604	81,821
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	70,473	68,071	66,774
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	15,131	13,750	11,294
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	13,328	11,657
Held For Investment Mortgage Finance Receivables Interest Only Mortgage Loans	$ 18	20
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | 2019 or sooner [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest-only mortgage loan portfolio principal amortization	36.00%
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | 2020, or sooner [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest-only mortgage loan portfolio principal amortization	48.00%
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 1,803	2,093
Held For Investment Mortgage Finance Receivables Interest Only Mortgage Loans	$ 416	496
Held For Investment Mortgage Finance Receivables Exited Interest Only Mortgage Loans	99.00%
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 39,940	41,072	$ 42,460
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	31,501	33,025
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	4,027	3,887
Commercial Portfolio Segment [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 4,412	$ 4,160

Finance Receivables and Loans68

Finance Receivables and Loans, Net (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Financing Receivable, Allowance for Credit Losses	$ 1,278	$ 1,155	$ 1,276	$ 1,144
Allowance for Loan and Lease Losses, Write-offs	(306)	(296)	(683)	(646)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	126	97	244	194
Allowance for Loan and Lease Losses Write-offs, Net	(180)	(199)	(439)	(452)
Provision for Loan Losses Expensed	158	269	419	540
Allowance for Loan and Lease Losses, Adjustments, Other	(1)		(1)	7
Financing Receivable, Allowance for Credit Losses	1,257	1,225	1,257	1,225
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	93	97	93	97
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,164	1,128	1,164	1,128
Loans and Leases Receivable, Gross	125,544	120,528	125,544	120,528	$ 122,893
Financing Receivable, Individually Evaluated for Impairment	906	773	906	773
Financing Receivable, Collectively Evaluated for Impairment	124,638	119,755	124,638	119,755
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Financing Receivable, Allowance for Credit Losses	1,066	941	1,066	932
Allowance for Loan and Lease Losses, Write-offs	(296)	(290)	(661)	(631)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	114	91	226	181
Allowance for Loan and Lease Losses Write-offs, Net	(182)	(199)	(435)	(450)
Provision for Loan Losses Expensed	168	260	421	527
Allowance for Loan and Lease Losses, Adjustments, Other	(1)		(1)	7
Financing Receivable, Allowance for Credit Losses	1,053	1,002	1,053	1,002
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	42	34	42	34
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,011	968	1,011	968
Loans and Leases Receivable, Gross	70,473	66,774	70,473	66,774	68,071
Financing Receivable, Individually Evaluated for Impairment	480	380	480	380
Financing Receivable, Collectively Evaluated for Impairment	69,993	66,394	69,993	66,394
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Financing Receivable, Allowance for Credit Losses	74	86	79	91
Allowance for Loan and Lease Losses, Write-offs	(8)	(6)	(20)	(15)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	6	6	12	13
Allowance for Loan and Lease Losses Write-offs, Net	(2)	0	(8)	(2)
Provision for Loan Losses Expensed	(4)	(3)	(3)	(6)
Allowance for Loan and Lease Losses, Adjustments, Other	2		2	0
Financing Receivable, Allowance for Credit Losses	66	83	66	83
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	24	31	24	31
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	42	52	42	52
Loans and Leases Receivable, Gross	15,131	11,294	15,131	11,294	13,750
Financing Receivable, Individually Evaluated for Impairment	228	242	228	242
Financing Receivable, Collectively Evaluated for Impairment	14,903	11,052	14,903	11,052
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Financing Receivable, Allowance for Credit Losses	138	128	131	121
Allowance for Loan and Lease Losses, Write-offs	(2)	0	(2)	0
Allowance for Loan and Lease Loss, Recovery of Bad Debts	6	0	6	0
Allowance for Loan and Lease Losses Write-offs, Net	4	0	4	0
Provision for Loan Losses Expensed	(6)	12	1	19
Allowance for Loan and Lease Losses, Adjustments, Other	(2)		(2)	0
Financing Receivable, Allowance for Credit Losses	138	140	138	140
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	27	32	27	32
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	111	108	111	108
Loans and Leases Receivable, Gross	39,940	42,460	39,940	42,460	$ 41,072
Financing Receivable, Individually Evaluated for Impairment	198	151	198	151
Financing Receivable, Collectively Evaluated for Impairment	$ 39,742	$ 42,309	$ 39,742	$ 42,309

Finance Receivables and Loans69

Finance Receivables and Loans, Net (Schedule of Sales of Financing Receivables and Loans) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Sales and Transfers	$ 4	$ 88	$ 5	$ 1,304
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Sales and Transfers	0	85	0	1,298
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Sales and Transfers	$ 4	$ 3	$ 5	$ 6

Finance Receivables and Loans70

Finance Receivables and Loans, Net (Schedule of Purchases of Financing Receivables and Loans) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Purchases	$ 1,085	$ 1,420	$ 2,548	$ 1,815
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Purchases	233	611	401	679
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Significant Purchases	$ 852	$ 809	$ 2,147	$ 1,136

Finance Receivables and Loans71

Finance Receivables and Loans, Net (Past Due Financing Receivables and Loans) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 2,537	$ 2,967
Financing Receivable, Recorded Investment, Current	123,007	119,926
Loans and Leases Receivable, Gross	125,544	122,893	$ 120,528
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,512	2,959
Financing Receivable, Recorded Investment, Current	83,092	78,862
Loans and Leases Receivable, Gross	85,604	81,821
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,341	2,740
Financing Receivable, Recorded Investment, Current	68,132	65,331
Loans and Leases Receivable, Gross	70,473	68,071	66,774
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	171	219
Financing Receivable, Recorded Investment, Current	14,960	13,531
Loans and Leases Receivable, Gross	15,131	13,750	11,294
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	65	89
Financing Receivable, Recorded Investment, Current	13,263	11,568
Loans and Leases Receivable, Gross	13,328	11,657
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	106	130
Financing Receivable, Recorded Investment, Current	1,697	1,963
Loans and Leases Receivable, Gross	1,803	2,093
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	25	8
Financing Receivable, Recorded Investment, Current	39,915	41,064
Loans and Leases Receivable, Gross	39,940	41,072	$ 42,460
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	21	8
Financing Receivable, Recorded Investment, Current	31,480	33,017
Loans and Leases Receivable, Gross	31,501	33,025
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	4	0
Financing Receivable, Recorded Investment, Current	4,023	3,887
Loans and Leases Receivable, Gross	4,027	3,887
Commercial Portfolio Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Financing Receivable, Recorded Investment, Current	4,412	4,160
Loans and Leases Receivable, Gross	4,412	4,160
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,798	2,102
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	1,794	2,097
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	1,706	1,994
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	88	103
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	50	60
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	38	43
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	4	5
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	0	5
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	4	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Real Estate [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]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	405	514
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	405	514
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	387	478
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	18	36
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	4	11
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	14	25
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 [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	334	351
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	313	348
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	248	268
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	65	80
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	11	18
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	54	62
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	3
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	21	3
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	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Real Estate [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	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 905	$ 792
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	707	720
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	602	603
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	105	117
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	18	25
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	87	92
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	198	72
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	88	27
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	104	44
Commercial Portfolio Segment [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 6	$ 1

Finance Receivables and Loans73

Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 125,544	$ 122,893	$ 120,528
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	85,604	81,821
Consumer Portfolio Segment [Member] | Consumer Loan [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	84,897	81,101
Consumer Portfolio Segment [Member] | Consumer Loan [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	707	720
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	70,473	68,071	66,774
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	69,871	67,468
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	602	603
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	15,131	13,750	$ 11,294
Consumer Portfolio Segment [Member] | Residential Mortgage [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	15,026	13,633
Consumer Portfolio Segment [Member] | Residential Mortgage [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	105	117
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	13,328	11,657
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	13,310	11,632
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	18	25
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,803	2,093
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	1,716	2,001
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 87	$ 92

Finance Receivables and Loans74

Finance Receivables and Loans, Net (Schedule of Pass And Criticized Credit Quality Indicators of Finance Receivables) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 125,544	$ 122,893	$ 120,528
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	39,940	41,072	$ 42,460
Commercial Portfolio Segment [Member] | Commercial Loan [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	36,343	37,991
Commercial Portfolio Segment [Member] | Commercial Loan [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	3,597	3,081
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	31,501	33,025
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	28,890	30,982
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,611	2,043
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	4,027	3,887
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	3,260	2,986
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	767	901
Commercial Portfolio Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	4,412	4,160
Commercial Portfolio Segment [Member] | Commercial Real Estate [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	4,193	4,023
Commercial Portfolio Segment [Member] | Commercial Real Estate [Member] | Criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 219	$ 137

Finance Receivables and Loans75

Finance Receivables and Loans, Net (Impaired Financing Receivables) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	$ 934	$ 756
Impaired Financing Receivable, Recorded Investment	906	733
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	244	172
Impaired Financing Receivable, with Related Allowance, Recorded Investment	662	561
Impaired Financing Receivable, Related Allowance	93	77
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	724	674
Impaired Financing Receivable, Recorded Investment	708	661
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	184	153
Impaired Financing Receivable, with Related Allowance, Recorded Investment	524	508
Impaired Financing Receivable, Related Allowance	66	63
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	491	438
Impaired Financing Receivable, Recorded Investment	480	430
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	117	91
Impaired Financing Receivable, with Related Allowance, Recorded Investment	363	339
Impaired Financing Receivable, Related Allowance	42	36
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	233	236
Impaired Financing Receivable, Recorded Investment	228	231
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	67	62
Impaired Financing Receivable, with Related Allowance, Recorded Investment	161	169
Impaired Financing Receivable, Related Allowance	24	27
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	10	8
Impaired Financing Receivable, Recorded Investment	10	8
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4	4
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6	4
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	223	228
Impaired Financing Receivable, Recorded Investment	218	223
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	63	58
Impaired Financing Receivable, with Related Allowance, Recorded Investment	155	165
Impaired Financing Receivable, Related Allowance	24	27
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	210	82
Impaired Financing Receivable, Recorded Investment	198	72
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	60	19
Impaired Financing Receivable, with Related Allowance, Recorded Investment	138	53
Impaired Financing Receivable, Related Allowance	27	14
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	88	27
Impaired Financing Receivable, Recorded Investment	88	27
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	16	9
Impaired Financing Receivable, with Related Allowance, Recorded Investment	72	18
Impaired Financing Receivable, Related Allowance	12	3
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	116	54
Impaired Financing Receivable, Recorded Investment	104	44
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	40	10
Impaired Financing Receivable, with Related Allowance, Recorded Investment	64	34
Impaired Financing Receivable, Related Allowance	15	11
Commercial Portfolio Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance	6	1
Impaired Financing Receivable, Recorded Investment	6	1
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2	1
Impaired Financing Receivable, Related Allowance	$ 0	$ 0

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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 865	$ 770	$ 822	$ 758
Impaired Financing Receivable, Interest Income, Accrual Method	11	17	21	24
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	700	637	691	628
Impaired Financing Receivable, Interest Income, Accrual Method	10	8	19	15
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	472	391	462	381
Impaired Financing Receivable, Interest Income, Accrual Method	7	5	14	10
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	228	246	229	247
Impaired Financing Receivable, Interest Income, Accrual Method	3	3	5	5
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	9	8	9	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	219	238	220	239
Impaired Financing Receivable, Interest Income, Accrual Method	3	3	5	5
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	165	133	131	130
Impaired Financing Receivable, Interest Income, Accrual Method	1	9	2	9
Commercial Portfolio Segment [Member] | Commercial And Industrial Automobile [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	78	54	61	47
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	82	73	66	77
Impaired Financing Receivable, Interest Income, Accrual Method	0	8	0	8
Commercial Portfolio Segment [Member] | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment	5	6	4	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		6 Months Ended
	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	$ 791		$ 791		$ 712
Loans and Leases Receivable, Impaired, Commitment to Lend	$ 7		$ 7		$ 6
Financing Receivable, Modifications, Number of Contracts	5,937	5,782	13,042	12,284
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 174	$ 127	$ 313	$ 277
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 157	$ 111	$ 277	$ 245
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	5,932	5,781	13,037	12,282
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 115	$ 106	$ 254	$ 233
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 102	$ 90	$ 222	$ 201
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	5,898	5,762	12,940	12,209
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 107	$ 103	$ 235	$ 218
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 93	$ 88	$ 203	$ 187
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	34	19	97	73
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 8	$ 3	$ 19	$ 15
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 9	$ 2	$ 19	$ 14
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	7	0	8	1
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 2	$ 0	$ 3	$ 0
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 2	$ 0	$ 3	$ 0
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	27	19	89	72
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 6	$ 3	$ 16	$ 15
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 7	$ 2	$ 16	$ 14
Commercial Portfolio Segment [Member] | Commercial Loan [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	5	1	5	2
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 59	$ 21	$ 59	$ 44
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 55	$ 21	$ 55	$ 44
Commercial Portfolio Segment [Member] | Commercial And Industrial Other [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	2	1	2	2
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 55	$ 21	$ 55	$ 44
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 51	$ 21	$ 51	$ 44
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	$ 4	$ 0	$ 4	$ 0
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 4	$ 0	$ 4	$ 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		6 Months Ended
	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	2,426	2,143	4,752	4,133
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 29	$ 25	$ 57	$ 50
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 17	$ 17	$ 35	$ 33
Automobile Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	2,425	2,143	4,751	4,132
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 29	$ 25	$ 57	$ 49
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 17	$ 17	$ 35	$ 33
Mortgage Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0	0	1
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 0	$ 0	$ 0	$ 1
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	0	1	0
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	Jun. 30, 2018	Dec. 31, 2017
Leases, Operating [Abstract]
Property Subject to or Available for Operating Lease, Gross	$ 10,260	$ 10,556
Property Subject to or Available for Operating Lease, Accumulated Depreciation	(1,621)	(1,815)
Property Subject to or Available for Operating Lease, Net	$ 8,639	$ 8,741

Investment in Operating Lease80

Investment in Operating Leases, Net (Schedule Of Depreciation Expense On Operating Lease Assets) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Leases, Operating [Abstract]
Depreciation Expense On Operating Lease Assets	$ 281	$ 353	$ 572	$ 739
Gross Remarketing (Gains) Losses	(16)	(32)	(34)	(29)
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	$ 265	$ 321	$ 538	$ 710

Securitizations and Variable 81

Securitizations and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
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	$ 0	$ 0	$ 2
Assets of nonconsolidated variable interest entities	1,388		1,388		$ 1,964
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	2,384		2,384		2,791
Carrying value of assets for VIEs for which we have continuing involvement	29,518		29,518		30,776
Carrying value of liabilities for VIEs for which we have continuing involvement	12,726		12,726		10,483
Commercial Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	739		739		592
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	344		344		248
Assets of nonconsolidated variable interest entities	0		0		0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	968		968		790
Automobile Loan [Member] | Consumer Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	18,806		18,806		17,597
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	8,787		8,787		7,677
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	28		28		37
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	0		0		0
Assets of nonconsolidated variable interest entities	1,388		1,388		1,964
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	1,416		1,416		2,001
Automobile Loan [Member] | Consumer Portfolio Segment [Member] | Held-to-maturity Securities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	27		27		36
Automobile Loan [Member] | Consumer Portfolio Segment [Member] | Other Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	1		1		1
Automobile Loan [Member] | Commercial Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	9,945		9,945		12,550
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	3,595		3,595		2,558
Unencumbered [Member] | Automobile Loan [Member] | Consumer Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	8,500		8,500		8,500
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 25		$ 25		$ 29

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] - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Automobile Loan [Member]
Cash Flow Received and Paid to Nonconsolidated Securitization Entities [Line Items]
Cash Flows Between Transferor and Transferee, Purchases of Previously Transferred Financial Assets	$ (2)	$ (491)
Cash Flows Between Transferor and Transferee, Servicing Fees	10	18
Cash Flows Between Transferor and Transferee, Beneficial Interest	9	10
Cash Flow Between Transferee and Transferor Representations And Warranties Obligations	0
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers		1,187
Cash Flows Between Transferor and Transferee, Receipts on Transferor's Interest in Transferred Financial Assets, Other		4
Residential Mortgage [Member]
Cash Flow Received and Paid to Nonconsolidated Securitization Entities [Line Items]
Cash Flows Between Transferor and Transferee, Purchases of Previously Transferred Financial Assets	0	0
Cash Flows Between Transferor and Transferee, Servicing Fees	0	0
Cash Flows Between Transferor and Transferee, Beneficial Interest	0	0
Cash Flow Between Transferee and Transferor Representations And Warranties Obligations	$ 2
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers		0
Cash Flows Between Transferor and Transferee, Receipts on Transferor's Interest in Transferred Financial Assets, Other		$ 0

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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
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	$ 2,352		$ 2,352		$ 3,363
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	15		15		20
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	2	$ 4	6	$ 8
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	1,388		1,388		1,964
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	12		12		16
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	2	3	5	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	1,388		1,388		1,964
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	12		12		16
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	2	3	5	6
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	964		964		1,399
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	3		3		$ 4
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	$ 0	$ 1	$ 1	$ 2

Servicing Activities (Schedule

Servicing Activities (Schedule of Total Serviced Automobile Loans Outstanding) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Automobile Serviced Assets [Line Items]
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	$ 8	$ 14	$ 16	$ 30
Total Primary Serviced Assets	116,431		116,431		$ 116,878
Consumer Loan [Member] | On-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	69,701		69,701		67,631
Commercial Loan [Member] | On-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	35,645		35,645		37,058
Operating Leases [Member] | On-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	8,613		8,613		8,682
Other Assets [Member] | On-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	111		111		121
Asset-backed Securities, Securitized Loans and Receivables [Member] | Off-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	1,392		1,392		1,977
Whole-Loan Transactions [Member] | Off-Balance Sheet Loans [Member]
Automobile Serviced Assets [Line Items]
Total Primary Serviced Assets	$ 969		$ 969		$ 1,409

Other Assets (Schedule of Other

Other Assets (Schedule of Other Assets) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Other Assets [Abstract]
Property, Plant and Equipment, Gross	$ 1,161	$ 1,161	$ 1,064
Accumulated Depreciation, Depletion and Amortization, Property Plant and Equipment	(648)	(648)	(608)
Property, Plant and Equipment, Net	513	513	456
Nonmarketable equity securities	1,276	1,276	1,233
Restricted cash collections for securitization trusts	796	796	812
Interest Receivable	548	548	550
Deferred Tax Assets, Net	455	455	461
Accounts and Other Receivables, Net, Current	289	289	116
Goodwill	240	240	240
Restricted Cash and Cash Equivalents	116	116	94
Cash reserve deposits held for securitization trusts	103	103	111
Derivative Asset, Fair Value, Gross Asset	63	63	39
Cash and securities collateral placed with counterparties	35	35	29
Other Assets, Miscellaneous	1,580	1,580	1,522
Other Assets	6,014	6,014	5,663
Federal Home Loan Bank Stock	790	790	745
Federal Reserve Bank Stock	447	447	445
Equity Securities without a Readily Determinable Fair Value	39	39
Goodwill [Line Items]
Goodwill	240	240	240
Equity Securities without a Readily Determinable Fair Value, Impairment	1	1
Insurance Operations [Member]
Other Assets [Abstract]
Goodwill	27	27	27
Goodwill [Line Items]
Goodwill	27	27	27
Corporate and Other [Member]
Other Assets [Abstract]
Goodwill	193	193	193
Goodwill [Line Items]
Goodwill	193	193	193
Automotive Finance Operations [Member]
Other Assets [Abstract]
Goodwill	20	20	20
Goodwill [Line Items]
Goodwill	$ 20	$ 20	$ 20

Deposit Liabilities (Schedule o

Deposit Liabilities (Schedule of Deposit Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Deposits [Abstract]
Noninterest-bearing deposit liabilities	$ 153	$ 108
Interest-bearing Deposit Liabilities, by Component [Abstract]
Deposits, Savings Deposits	50,958	49,267
Time Deposits	47,617	43,869
Dealer deposits	6	12
Deposits	98,734	93,256
Time Deposits, $100,000 or More	19,900	18,900
Time Deposits, at or Above FDIC Insurance Limit	$ 5,300	$ 5,300

Debt (Schedule of Short-term De

Debt (Schedule of Short-term Debt) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Demand Notes	$ 2,666	$ 3,171
Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months	3,475	7,350
Securities Sold under Agreements to Repurchase, Gross	967	892
Short-term Debt	7,108	11,413
Non-derivative Cash Collateral Placed with Counterparties Associated with the Repurchase Agreements	4	10
Non-derivative Cash Collateral received from counterparties associated with Repurchase Agreements	1	1
Non-derivative Noncash Collateral received from counterparties associated with Repurchase Agreements	1
Unsecured Debt [Member]
Short-term Debt [Line Items]
Demand Notes	2,666	3,171
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	2,666	3,171
Secured Debt [Member]
Short-term Debt [Line Items]
Demand Notes	0	0
Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months	3,475	7,350
Securities Sold under Agreements to Repurchase, Gross	967	892
Short-term Debt	4,442	$ 8,242
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	530
Maturity 61 to 90 Days [Member] | Secured Debt [Member]
Short-term Debt [Line Items]
Mortgage-backed Residential Securities Sold under Agreements to Repurchase, Maturity Period	437
US Treasury and Government [Member] | Maturity less than 90 Days [Member] | Secured Debt [Member]
Short-term Debt [Line Items]
Mortgage-backed Residential Securities Sold under Agreements to Repurchase, Maturity Period	276
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Maturity less than 90 Days [Member] | Secured Debt [Member]
Short-term Debt [Line Items]
Mortgage-backed Residential Securities Sold under Agreements to Repurchase, Maturity Period	$ 691

Debt (Long-term Debt) (Details)

Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	$ 10,756	$ 10,981
Long-term Debt, Excluding Current Maturities	36,473	33,037
Long-term Debt	47,328	44,226
Trust preferred securities	2,600	2,600
Secured Debt	37,723	36,837
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	2,740	3,482
Long-term Debt, Excluding Current Maturities	11,139	11,909
Long-term Debt	14,047	15,631
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	8,016	7,499
Long-term Debt, Excluding Current Maturities	25,334	21,128
Long-term Debt	33,281	28,595
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Secured Debt	14,700	10,300
Fair Value Hedging [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value Hedge Basis Adjustment	99	208
Long-term Debt	99	208
Fair Value Hedging [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value Hedge Basis Adjustment	168	240
Fair Value Hedging [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value Hedge Basis Adjustment	$ (69)	$ (32)

Debt (Scheduled Remaining Matur

Debt (Scheduled Remaining Maturity of Long-term Debt) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 5,295
Long-term Debt, Maturities, Repayments of Principal in Year Two	9,638
Long-term Debt, Maturities, Repayments of Principal in Year Three	9,642
Long-term Debt, Maturities, Repayments of Principal in Year Four	9,104
Long-term Debt, Maturities, Repayments of Principal in Year Five	5,581
Long-term Debt, Maturities, Repayments of Principal after Year Five	7,969
Derivative, Amount of Hedged Item	99
Long-term Debt	47,328	$ 44,226
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	1,939
Long-term Debt, Maturities, Repayments of Principal in Year Two	1,643
Long-term Debt, Maturities, Repayments of Principal in Year Three	2,212
Long-term Debt, Maturities, Repayments of Principal in Year Four	620
Long-term Debt, Maturities, Repayments of Principal in Year Five	1,019
Long-term Debt, Maturities, Repayments of Principal after Year Five	6,446
Derivative, Amount of Hedged Item	168
Long-term Debt	14,047	15,631
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt	33,281	$ 28,595
Long-term Debt [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	1,991
Long-term Debt, Maturities, Repayments of Principal in Year Two	1,681
Long-term Debt, Maturities, Repayments of Principal in Year Three	2,251
Long-term Debt, Maturities, Repayments of Principal in Year Four	663
Long-term Debt, Maturities, Repayments of Principal in Year Five	1,066
Long-term Debt, Maturities, Repayments of Principal after Year Five	7,414
Derivative, Amount of Hedged Item	168
Long-term Debt	15,234
Long-term Debt [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	3,356
Long-term Debt, Maturities, Repayments of Principal in Year Two	7,995
Long-term Debt, Maturities, Repayments of Principal in Year Three	7,430
Long-term Debt, Maturities, Repayments of Principal in Year Four	8,484
Long-term Debt, Maturities, Repayments of Principal in Year Five	4,562
Long-term Debt, Maturities, Repayments of Principal after Year Five	1,523
Derivative, Amount of Hedged Item	(69)
Long-term Debt	33,281
original issue discount [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Derivative, Amount of Hedged Item	0
Debt Instrument, Unamortized Discount, Current	(52)
Debt Instrument, Unamortized Discount	(1,187)
original issue discount [Member] | Unsecured Debt [Member] | Debt Instrument, Redemption, Period Two [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount, Noncurrent	(38)
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	(47)
original issue discount [Member] | Unsecured Debt [Member] | Debt Instrument, Redemption, Period Six [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount, Noncurrent	$ (968)

Debt (Pledged Assets Related to

Debt (Pledged Assets Related to Secured Borrowings and Repurchase Agreement) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Pledged Assets related to secured borrowings [Line Items]
Pledged Financial Instruments, Not Separately Reported, Other Debt Securities Available-for-sale or Held-for-investment	$ 7,902	$ 8,371
Pledged Assets, Mortgage assets held for investment	14,943	13,579
Pledged Assets, Investment in operating leases	267	457
Pledged Assets, Other, Not Separately Reported on Statement of Financial Position	56,329	58,761
Secured Debt	37,723	36,837
Short-term Debt	7,108	11,413
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	6,995	7,443
Pledged Assets, Mortgage assets held for investment	14,943	13,579
Pledged Assets, Investment in operating leases	0	0
Pledged Assets, Other, Not Separately Reported on Statement of Financial Position	45,770	43,694
Secured Debt	27,990	23,278
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	26,300	25,200
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	2,400	2,300
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Pledged Assets related to secured borrowings [Line Items]
Pledged Assets, Not Separately Reported, Finance Receivables	18,965	19,787
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	9,621	6,200
Commercial Portfolio Segment [Member] | Automobile Loan [Member]
Pledged Assets related to secured borrowings [Line Items]
Pledged Assets, Not Separately Reported, Finance Receivables	14,252	16,567
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	$ 14,211	$ 16,472

Debt (Narrative - Trust Preferr

Debt (Narrative - Trust Preferred Securities) (Details) $ / shares in Units, $ in Billions	Jun. 30, 2018USD ($)$ / shares	Dec. 31, 2017USD ($)
Narrative - Trust Preferred Securities [Line Items]
Trust preferred securities	$ 2.6	$ 2.6
Debt Instrument, Interest Rate, Stated Percentage	8.125%
Preferred Stock, Liquidation Preference Per Share | $ / shares	$ 25
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 at anytime on or before February 15, 2040.	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	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Outstanding Revolving Funding Facilities	$ 9,200
Long-term Line of Credit	6,355	$ 8,115
Line of Credit Facility, Remaining Borrowing Capacity	2,870	3,810
Line of Credit Facility, Maximum Borrowing Capacity	9,225	11,925
Ally Bank [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	2,500	1,785
Line of Credit Facility, Remaining Borrowing Capacity	0	890
Line of Credit Facility, Maximum Borrowing Capacity	2,500	2,675
Revolving secured funding facilities 1 year or greater [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	7,600
Nonbank Funding [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	3,855	6,330
Line of Credit Facility, Remaining Borrowing Capacity	2,870	2,920
Line of Credit Facility, Maximum Borrowing Capacity	$ 6,725	$ 9,250

Accrued Expenses and Other Li93

Accrued Expenses and Other Liabilities (Schedule of Accrued Expenses and Other Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounts Payable and Accrued Liabilities [Abstract]
Accounts Payable	$ 369	$ 746
Accrued Employee Benefits	188	248
Liability for Claims and Claims Adjustment Expense	149	140	$ 179	$ 149
Derivative Liability, Fair Value, Gross Liability	65	41
Cash collateral received from counterparties	39	17
Deferred Revenue	28	32
Other Accrued Liabilities	673	556
Accounts Payable and Accrued Liabilities	$ 1,511	$ 1,780

Accumulated Other Comprehensi94

Accumulated Other Comprehensive Loss (Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	$ (598)	$ (177)	$ (598)	$ (177)	$ (186)	$ (173)	$ (273)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(74)	75	(412)	96
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	19	14	19	14	20	16	14
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax			(1)	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	28	9	28	9	11	11	8
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	3	1	17	1
Other Comprehensive Income (Loss), Defined Benefit Plan, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	97	91	97	91	95	89	90
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	(1)		2	1
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax	648	245	648	245	250	$ 235	$ 341
Other Comprehensive Income (Loss), Net of Tax	$ (70)	$ 76	$ (398)	$ 96
Accounting Standards Update 2016-01 [Member]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax					27
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax					0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax					0
Other Comprehensive Income (Loss), Defined Benefit Plan, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax					0
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax					(27)
Accounting Standards Update 2018-02 [Member]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax					(40)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax					4
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax					0
Other Comprehensive Income (Loss), Defined Benefit Plan, Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax					6
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax					$ 42

Accumulated Other Comprehensi95

Accumulated Other Comprehensive Loss (Before and After Tax) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
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)	$ 132	$ (531)	$ 183
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	1	23	7	50
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax	(96)	109	(538)	133
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	(37)	125	(42)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	0	(3)	(1)	(5)
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax	22	(34)	126	(37)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax [Abstract]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	(73)	95	(406)	141
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	1	20	6	45
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(74)	75	(412)	96
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	(3)	4	(8)	6
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax [Abstract]
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	1	(1)	2	(2)
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, Net of Tax	(2)	3	(6)	4
Other Comprehensive Income (Loss), Net investment hedges, before Tax [Abstract]
Other Comprehensive Income Unrealized Gain Loss On Net Investment Hedges Arising During the Period, Before Tax	3	(4)	7	(6)
Other Comprehensive Income (Loss), Net investment hedges, Tax [Abstract]
Other Comprehensive Income Unrealized Gain Loss On Net Investment Hedges Arising During the Period, Tax	(1)	1	(2)	2
Other Comprehensive Income (Loss), Net investment hedges, Net of Tax [Abstract]
Other Comprehensive Income Unrealized Gain Loss On Net Investment Hedges Arising During the Period Net of Tax	2	(3)	5	(4)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax [Abstract]
Other Comprehensive Income Unrealized Gain Loss On Cash Flow Hedges Arising During the Period, Before Tax	5	1	23	1
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax Effect [Abstract]
Other Comprehensive Income Unrealized Gain Loss On Cash Flow Hedges Arising During the Period, Tax	(2)	0	(6)	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	3	1	17	1
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Tax [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	1		(2)	(1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Tax [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax	0		0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Net of Tax [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax	1		(2)	(1)
Other Comprehensive Income (Loss), before Tax [Abstract]
Other Comprehensive Income (Loss), before Tax	(90)	110	(518)	133
Other Comprehensive Income (Loss), Tax [Abstract]
Other Comprehensive Income (Loss), Tax	20	(34)	120	(37)
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), Net of Tax	$ (70)	$ 76	$ (398)	$ 96

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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	$ 348	$ 254	$ 600	$ 467
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	1	(2)	(1)	(1)
Net Income (Loss) Attributable to Parent	$ 349	$ 252	$ 599	$ 466
Weighted Average Number of Shares Outstanding, Basic	430,628	457,891	433,405	461,904
Weighted Average Number of Shares Outstanding, Diluted	432,554	458,819	435,727	462,802
Earnings Per Share, Basic [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.81	$ 0.55	$ 1.38	$ 1.01
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	(0.01)	0	0
Earnings Per Share, Basic	0.81	0.55	1.38	1.01
Earnings Per Share, Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Diluted Share	0.80	0.55	1.38	1.01
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	(0.01)	0	0
Earnings Per Share, Diluted	$ 0.81	$ 0.55	$ 1.37	$ 1.01

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	Jul. 13, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Aug. 22, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 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%
Tier One Leverage Capital Required for Capital Adequacy to Average Assets		4.00%
BHC Enhanced Prudential Standards, Minimum		$ 100,000
BHC Enhanced Prudential Standards, Maximum		250,000
BHC Stress Test Threshold		50,000
Federal Reserve Bank Stock		$ 447		$ 445
Minimum Capital Conservation Buffer		1.875%		1.25%
Increased Minimum Capital Conservation Buffer		2.50%
Increase (decrease) in share repurchase program		32.00%
Stock Repurchase Program, Authorized Amount		$ 1,000
Dividends Payable, Amount Per Share		$ 0.13	$ 0.13	$ 0.12	$ 0.12		$ 0.08	$ 0.08	$ 0.08	$ 0.08
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		$ 13,265		$ 13,237
Percentage of Common Equity Tier 1 Capital to Risk-weighted Assets		9.37%		9.53%
Tier One Risk Based Capital		$ 15,698		$ 15,628
Tier One Risk Based Capital to Risk Weighted Assets		11.09%		11.25%
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets		6.00%
Capital		$ 17,926		$ 17,974
Capital to Risk Weighted Assets		12.66%		12.94%
Capital Required to be Well Capitalized to Risk Weighted Assets		10.00%
Tier One Leverage Capital		$ 15,698		$ 15,628
Tier One Leverage Capital to Average Assets		9.21%		9.53%
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		$ 16,591		$ 17,059
Percentage of Common Equity Tier 1 Capital to Risk-weighted Assets		13.65%		15.04%
Common Equity Tier 1 Capital Required to be Well Capitalized to Risk-weighted Assets		6.50%
Tier One Risk Based Capital		$ 16,591		$ 17,059
Tier One Risk Based Capital to Risk Weighted Assets		13.65%		15.04%
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets		8.00%
Capital		$ 17,557		$ 17,886
Capital to Risk Weighted Assets		14.45%		15.77%
Capital Required to be Well Capitalized to Risk Weighted Assets		10.00%
Tier One Leverage Capital		$ 16,591		$ 17,059
Tier One Leverage Capital to Average Assets		11.50%		12.87%
Tier One Leverage Capital Required to be Well Capitalized to Average Assets		5.00%
Subsequent Event [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Dividends Payable, Amount Per Share	$ 0.15
Increase (Decrease) in Dividends Payable, per share	$ 0.02
Increase (Decrease) in Dividends Payable	15.00%

Regulatory Capital and Other 98

Regulatory Capital and Other Regulatory Matters (Common Share Repurchases) (Details) - USD ($) $ / shares in Units, $ in Millions	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016
Accelerated Share Repurchases [Line Items]
Treasury Stock, Common, Value	$ 195	$ 185	$ 190	$ 190	$ 204	$ 169	$ 167	$ 159
Treasury Stock, Common, Shares	7,280,000	6,473,000	7,033,000	8,507,000	10,485,000	8,097,000	8,745,000	8,298,000
Common Stock, Shares, Outstanding			437,053,936
Dividends Payable, Amount Per Share	$ 0.13	$ 0.13	$ 0.12	$ 0.12	$ 0.08	$ 0.08	$ 0.08	$ 0.08
Beginning of Period [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding		432,691,000	437,054,000	443,796,000	452,292,000	462,193,000	467,000,000	475,470,000	483,753,000
End of Period [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding	425,752,000	432,691,000	437,054,000	443,796,000	452,292,000	462,193,000	467,000,000	475,470,000

Derivative Instruments and He99

Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash Collateral Placed with Counterparties Excluding Cash Collateral Associated with Repurchase Agreements	$ 31	$ 20
Securities Collateral Placed with Counterparties	151	97
Cash Collateral Received from Counterparties, Excluding Collateral Associated with Repurchase Agreements	38	17
Non-cash collateral received from Counterparties	$ 11	$ 2

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	Jun. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 63	$ 39
Derivative Liability, Fair Value, Gross Liability	65	41
Derivative, Notional Amount	42,641	23,762
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	1	1
Derivative, Notional Amount	28,985	7,051
Not Designated as Hedging Instrument [Member] | Other Trading [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	63	39
Derivative Liability, Fair Value, Gross Liability	64	40
Derivative, Notional Amount	13,656	16,711
Interest Rate Swap [Member] | 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	28,840	6,915
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	1	1
Derivative, Notional Amount	145	136
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	63	39
Derivative Liability, Fair Value, Gross Liability	62	39
Derivative, Notional Amount	13,463	16,587
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Futures and Forwards [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	9	23
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Written Options [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	1
Derivative Liability, Fair Value, Gross Liability	62	39
Derivative, Notional Amount	6,760	8,327
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Purchased Options [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	62	38
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	6,694	8,237
Foreign Exchange 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	1	1
Derivative, Notional Amount	193	124
Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	1	1
Derivative, Notional Amount	193	124
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	1	0
Derivative, Notional Amount	0	0
Equity Contract [Member] | Not Designated as Hedging Instrument [Member] | Written Options [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	1	0
Derivative, Notional Amount	$ 0	$ 0

Derivative Instruments and H101

Derivative Instruments and Hedging Activities (Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Long-term Debt	$ 47,328	$ 44,226
Last of Layer in the Hedge Relationship	17,700
Basis Adjustment - Last-of-Layer	51
Carrying Amount [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Available-for-sale Securities, Debt Securities	1,435	173
Financing Receivable, Net	41,383	2,305
Long-term Debt	14,959	14,640
Fair Value Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Available-for-sale Securities, Debt Securities	(3)	2
Financing Receivable, Net	(40)	18
Long-term Debt	99	208
Discontinued Hedge [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Available-for-sale Securities, Debt Securities	(2)	2
Financing Receivable, Net	11	19
Long-term Debt	$ 95	$ 235

Derivative Instruments and H102

Derivative Instruments and Hedging Activities (Statement of Gains and Losses on Derivative Instruments Reported in Statement of Comprehensive Income) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ 4	$ (3)	$ 6	$ (6)
Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(2)	0	0	(2)
Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	6	(3)	6	(4)
Other Income [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(2)	(1)	0	(3)
Other Income [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	6	(3)	6	(4)
Gains on Mortgage and Automotive Loans [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 0	$ 1	$ 0	$ 1

Derivative Instruments and H103

Derivative Instruments and Hedging Activities (Derivative Instruments Designated as Fair Value Hedges, Gain (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Interest and Fee Income, Loans and Leases	$ 1,647	$ 1,447	$ 3,190	$ 2,815
Interest and Dividend Income, Securities, Operating, Available-for-sale	188	146	364	280
Interest Expense, Long-term Debt	434	417	845	841
Designated as Hedging Instrument [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	0	0	0	(2)
Designated as Hedging Instrument [Member] | Interest and Dividends Income [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	0	0	0	0
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	0	0	1	1
Designated as Hedging Instrument [Member] | Unsecured Debt [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0	0	0
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	0	0	0	0
Designated as Hedging Instrument [Member] | Unsecured Debt [Member] | Interest and Dividends Income [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0	0	0
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	0	0	0	0
Designated as Hedging Instrument [Member] | Unsecured Debt [Member] | Interest Expense [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	8	(21)	44	(23)
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	(8)	21	(43)	24
Designated as Hedging Instrument [Member] | Federal Home Loan Bank Certificates and Obligations (FHLB) [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0	0	0
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	0	0	0	0
Designated as Hedging Instrument [Member] | Federal Home Loan Bank Certificates and Obligations (FHLB) [Member] | Interest and Dividends Income [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0	0	0
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	0	0	0	0
Designated as Hedging Instrument [Member] | Federal Home Loan Bank Certificates and Obligations (FHLB) [Member] | Interest Expense [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	10	1	43	0
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	(10)	(1)	(43)	0
Designated as Hedging Instrument [Member] | Available-for-sale Securities [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0	0	0
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	0	0	0	0
Designated as Hedging Instrument [Member] | Available-for-sale Securities [Member] | Interest and Dividends Income [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	(2)	2	(5)	2
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	2	(2)	5	(2)
Designated as Hedging Instrument [Member] | Available-for-sale Securities [Member] | Interest Expense [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0	0	0
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	0	0	0	0
Designated as Hedging Instrument [Member] | Fixed-rate Automotive Loans [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	(6)	1	(51)	(3)
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	6	(1)	51	1
Designated as Hedging Instrument [Member] | Fixed-rate Automotive Loans [Member] | Interest and Dividends Income [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0	0	0
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	0	0	0	0
Designated as Hedging Instrument [Member] | Fixed-rate Automotive Loans [Member] | Interest Expense [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	0	0	0	0
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	$ 0	$ 0	$ 0	$ 0

Derivative Instruments and H104

Derivative Instruments and Hedging Activities (Interest and Amortization on Derivative Instruments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Interest and Fee Income, Loans and Leases	$ 1,647	$ 1,447	$ 3,190	$ 2,815
Interest and Dividend Income, Securities, Operating, Available-for-sale	188	146	364	280
Interest Expense, Long-term Debt	434	417	845	841
Earnings on cash flow hedges to be recognized within twelve months	18		18
Designated as Hedging Instrument [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	0	0	0	(2)
Designated as Hedging Instrument [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	1	(6)	(10)	(12)
Designated as Hedging Instrument [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Amortization and Interest [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest for Qualifying Hedge	0	0	0	0
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net	0	0	0	0
Designated as Hedging Instrument [Member] | Interest and Dividends Income [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	0	0	0	0
Designated as Hedging Instrument [Member] | Interest and Dividends Income [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings			(1)	0
Designated as Hedging Instrument [Member] | Interest and Dividends Income [Member] | Amortization and Interest [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest for Qualifying Hedge			0	0
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net			0	0
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	0	0	1	1
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	12	27	31	51
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Amortization and Interest [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest for Qualifying Hedge	2	0	3	0
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net	2	0	3	0
Designated as Hedging Instrument [Member] | Unsecured Debt [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Amortization of Deferred Basis Adjustments	0	0	0	0
Gain (Loss) on Interest for Qualifying Hedge	0	0	0	0
Designated as Hedging Instrument [Member] | Unsecured Debt [Member] | Interest and Dividends Income [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Amortization of Deferred Basis Adjustments			0	0
Gain (Loss) on Interest for Qualifying Hedge			0	0
Designated as Hedging Instrument [Member] | Unsecured Debt [Member] | Interest Expense [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Amortization of Deferred Basis Adjustments	14	20	29	40
Gain (Loss) on Interest for Qualifying Hedge	1	7	4	12
Designated as Hedging Instrument [Member] | Federal Home Loan Bank Certificates and Obligations (FHLB) [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Amortization of Deferred Basis Adjustments	0	0	0	0
Gain (Loss) on Interest for Qualifying Hedge	0	0	0	0
Designated as Hedging Instrument [Member] | Federal Home Loan Bank Certificates and Obligations (FHLB) [Member] | Interest and Dividends Income [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Amortization of Deferred Basis Adjustments			0	0
Gain (Loss) on Interest for Qualifying Hedge			0	0
Designated as Hedging Instrument [Member] | Federal Home Loan Bank Certificates and Obligations (FHLB) [Member] | Interest Expense [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Amortization of Deferred Basis Adjustments	(5)	0	(6)	(1)
Gain (Loss) on Interest for Qualifying Hedge	2	0	4	0
Designated as Hedging Instrument [Member] | Available-for-sale Securities [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest for Qualifying Hedge			0	0
Designated as Hedging Instrument [Member] | Available-for-sale Securities [Member] | Interest and Dividends Income [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest for Qualifying Hedge			(1)	0
Designated as Hedging Instrument [Member] | Available-for-sale Securities [Member] | Interest Expense [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Interest for Qualifying Hedge			0	0
Designated as Hedging Instrument [Member] | Fixed-rate Automotive Loans [Member] | Interest and Fees on Finance Receivables and Loans [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Amortization of Deferred Basis Adjustments	(4)	(6)	(8)	(11)
Gain (Loss) on Interest for Qualifying Hedge	5	0	(2)	(1)
Designated as Hedging Instrument [Member] | Fixed-rate Automotive Loans [Member] | Interest and Dividends Income [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Amortization of Deferred Basis Adjustments			0	0
Gain (Loss) on Interest for Qualifying Hedge			0	0
Designated as Hedging Instrument [Member] | Fixed-rate Automotive Loans [Member] | Interest Expense [Member] | Amortization and Interest [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Amortization of Deferred Basis Adjustments	0	0	0	0
Gain (Loss) on Interest for Qualifying Hedge	$ 0	$ 0	$ 0	$ 0

Derivative Instruments and H105

Derivative Instruments and Hedging Activities (Derivative Instruments Used in Net Investment Hedge Accounting Relationships) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
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	$ 5	$ 1	$ 23	$ 1
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	$ 3	$ (4)	$ 7	$ (6)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018
Income Tax Disclosure [Abstract]
Income Tax Expense (Benefit)	$ 113	$ 122	$ 189	$ 235
Accounting Standards Update 2018-02 [Member]
Tax Act Impacts [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 42		$ 42		$ 0

Fair Value (Fair Value Measurem

Fair Value (Fair Value Measurements - Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities, Equity Securities	$ 521	$ 518
Available-for-sale securities	$ 23,296	$ 22,303
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	$ 23,296	$ 22,303
Derivative Assets	63	39
Assets, Fair Value Disclosure	23,897	22,878
Derivative Liability	(65)	(41)
Financial and Nonfinancial Liabilities, Fair Value Disclosure	65	41
Fair Value, Measurements, Recurring [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	(62)	(39)
Fair Value, Measurements, Recurring [Member] | Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	(2)	(2)
Fair Value, Measurements, Recurring [Member] | Other Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	(1)
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities, Equity Securities	521	518
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	1,874	1,777
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	854
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	154	154
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	15,066	14,291
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	2,625	2,494
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	642	541
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	868	936
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	1,216	1,256
Fair Value, Measurements, Recurring [Member] | Loans Held-for-Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	13	13
Fair Value, Measurements, Recurring [Member] | Retained Interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Retained Interest, Fair Value Disclosure	4	5
Fair Value, Measurements, Recurring [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	63	39
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	1,881	1,785
Derivative Assets	0	0
Assets, Fair Value Disclosure	2,390	2,303
Derivative Liability	(1)	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	1	0
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 Liability	0	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 Liability	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 Liability	(1)
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]
Marketable Securities, Equity Securities	509	518
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	1,874	1,777
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	7	8
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] | Loans Held-for-Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Retained Interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Retained Interest, Fair Value Disclosure	0	0
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	0	0
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	21,415	20,518
Derivative Assets	62	38
Assets, Fair Value Disclosure	21,477	20,556
Derivative Liability	(64)	(41)
Financial and Nonfinancial Liabilities, Fair Value Disclosure	64	41
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 Liability	(62)	(39)
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 Liability	(2)	(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 Liability	0
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]
Marketable Securities, Equity Securities	0	0
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	854
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	147	146
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	15,066	14,291
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	2,625	2,494
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	642	541
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	868	936
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	1,216	1,256
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Loans Held-for-Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Retained Interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Retained Interest, Fair Value Disclosure	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	62	38
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
Derivative Assets	1	1
Assets, Fair Value Disclosure	30	19
Derivative Liability	0	0
Financial and Nonfinancial 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 Liability	0	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 Liability	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 Liability	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]
Marketable Securities, Equity Securities	12	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] | Loans Held-for-Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgages Held-for-sale, Fair Value Disclosure	13	13
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Retained Interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Retained Interest, Fair Value Disclosure	4	5
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	$ 1

Fair Value (Fair Value Measu108

Fair Value (Fair Value Measurements - Reconciliation of Level 3 Assets And Liabilities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
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	$ 25	$ 32	$ 38	$ 29
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	1	2	(2)	2
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	73	20	132	23
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(68)	(14)	(134)	(12)
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	(1)	(31)	(4)	(33)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Assets, Ending balance	30	9	30	9
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	1	(5)	1
Equity Securities [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	12		19
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		(4)
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		(3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Assets, Ending balance	12		12
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0		(5)
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	7	1	13	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	1	0	2	0
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	73	20	132	23
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(68)	(18)	(134)	(20)
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	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Assets, Ending balance	13	3	13	3
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	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	5	29
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	1	0	1
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	4	0	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	(1)	(31)	(1)	(33)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Assets, Ending balance	4	5	4	5
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	1	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	1	0	1
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	0	0	0
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	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Assets, Ending balance	1	1	1	1
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 0	$ 1	$ 0	$ 1

Fair Value (Fair Value Measu109

Fair Value (Fair Value Measurements - Nonrecurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	$ 328	$ 108
Fair Value, Measurements, Nonrecurring [Member] | Loans Held-for-Sale [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	315	77
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	62	20
Lower of cost or fair value or valuation reserve allowance	(12)	(3)
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	50	22
Lower of cost or fair value or valuation reserve allowance	(15)	(12)
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	112	42
Lower of cost or fair value or valuation reserve allowance	(27)	(15)
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	14
Lower of cost or fair value or valuation reserve allowance	(1)	(1)
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
Lower of cost or fair value or valuation reserve allowance		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	440	136
Lower of cost or fair value or valuation reserve allowance	(28)	(16)
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] | Loans Held-for-Sale [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
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 [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
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 [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	315	77
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	62	20
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	50	22
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	112	42
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	14
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
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	$ 440	$ 136

Fair Value (Fair Value of Finan

Fair Value (Fair Value of Financial Instruments) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	$ 2,089	$ 1,899
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	328	108
Loans and Leases Receivable, Net Amount	124,287	121,617
Nonmarketable equity securities	1,276	1,233
Deposits	98,734	93,256
Short-term Debt	7,108	11,413
Long-term Debt	47,328	44,226
Carrying Value of Deposit Liabilities with no Defined Contractual Maturities		47,400
Fair Value of Deposit Liabilities With No Defined Contractual Maturities		45,200
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	2,089	1,899
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	315	95
Loans and Leases Receivable, Net Amount	124,287	121,617
Nonmarketable equity securities	1,237	1,233
Deposits	49,617	45,869
Short-term Debt	7,108	11,413
Long-term Debt	47,328	44,226
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	2,007	1,865
Loans and Leases Receivable, Net Amount	125,846	123,302
Nonmarketable equity securities	1,237	1,239
Short-term Debt	7,112	11,417
Long-term Debt	49,134	46,624
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 and Leases Receivable, Net Amount	0	0
Nonmarketable equity securities	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	2,007	1,865
Loans and Leases Receivable, Net Amount	0	0
Nonmarketable equity securities	1,237	1,190
Short-term Debt	0	0
Long-term Debt	28,040	27,807
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 and Leases Receivable, Net Amount	125,846	123,302
Nonmarketable equity securities	0	49
Short-term Debt	7,112	11,417
Long-term Debt	21,094	18,817
Portion at Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	315	95
Deposits	49,493	45,827
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0	0
Deposits	0	0
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0	0
Deposits	0	0
Portion at Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	315	95
Deposits	$ 49,493	$ 45,827

Offsetting Assets and Liabil111

Offsetting Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 63	$ 39
Derivative Liability, Fair Value, Gross Liability	65	41
Customer Securities for which Entity has Right to Sell or Repledge, Fair Value	11	2
Derivative assets in net asset position [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	62	38
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	62	38
Derivative Asset, Not Subject to Master Netting Arrangement	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset	62	38
Derivative assets with no offsetting arrangements [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	1
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1	1
Derivative Asset, Not Subject to Master Netting Arrangement	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset	1	1
Total Derivative Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	63	39
Gross Amounts Offset in the Condensed Consolidated Balance Sheet	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	63	39
Derivative Asset, Not Subject to Master Netting Arrangement	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset	63	39
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	65	41
Derivative Liability, Fair Value, Amount Offset Against Collateral	65	41
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	0
Derivative, Collateral, Right to Reclaim Cash	(1)	(1)
Derivative Liability	64	40
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	967	892
Derivative Liability, Fair Value, Amount Offset Against Collateral	967	892
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	0
Derivative, Collateral, Right to Reclaim Cash	(967)	(892)
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	1,032	933
Derivative Liability, Fair Value, Amount Offset Against Collateral	1,032	933
Derivative Liability, Not Subject to Master Netting Arrangement Deduction	0	0
Derivative, Collateral, Right to Reclaim Cash	(968)	(893)
Derivative Liability	$ 64	$ 40

Segment Information (Financial

Segment Information (Financial Information Operating Segments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net Financing Revenue	$ 1,094	$ 1,067	$ 2,143	$ 2,046
Nonoperating Income (Expense)	364	388	718	784
Revenue, Net	1,458	1,455	2,861	2,830
Provision for Loan Losses Expensed	158	269	419	540
Noninterest Expense	839	810	1,653	1,588
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	461	376	789	702
Assets	171,345	164,345	171,345	164,345	$ 167,148
Interest Income (Expense), after Provision for Loan Loss	936	798	1,724	1,506
Automotive Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	925	932	1,834	1,824
Nonoperating Income (Expense)	63	107	129	208
Revenue, Net	988	1,039	1,963	2,032
Provision for Loan Losses Expensed	170	266	429	534
Noninterest Expense	436	426	884	863
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	382	347	650	635
Assets	114,915	115,447	114,915	115,447
Insurance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	13	14	25	29
Nonoperating Income (Expense)	266	245	512	509
Revenue, Net	279	259	537	538
Provision for Loan Losses Expensed	0	0	0	0
Noninterest Expense	268	280	499	519
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	11	(21)	38	19
Assets	7,634	7,308	7,634	7,308
Mortgage Finance [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	44	32	87	66
Nonoperating Income (Expense)	2	1	3	1
Revenue, Net	46	33	90	67
Provision for Loan Losses Expensed	0	1	2	2
Noninterest Expense	32	25	66	49
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	14	7	22	16
Assets	13,385	8,902	13,385	8,902
Corporate Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	57	48	103	82
Nonoperating Income (Expense)	14	10	22	28
Revenue, Net	71	58	125	110
Provision for Loan Losses Expensed	(6)	6	(6)	12
Noninterest Expense	19	17	44	38
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	58	35	87	60
Assets	4,458	3,552	4,458	3,552
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	55	41	94	45
Nonoperating Income (Expense)	19	25	52	38
Revenue, Net	74	66	146	83
Provision for Loan Losses Expensed	(6)	(4)	(6)	(8)
Noninterest Expense	84	62	160	119
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(4)	8	(8)	(28)
Assets	$ 30,953	$ 29,136	$ 30,953	$ 29,136

Parent and Guarantor Condens113

Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	$ 1,647	$ 1,447	$ 3,190	$ 2,815
Interest and Fee Income, Loans and Leases Held-for-sale	6	0	6	0
Interest and Dividend Income, Securities, Operating	188	146	364	280
Interest Income, Deposits with Financial Institutions	17	7	32	12
Operating Leases, Income Statement, Lease Revenue	374	488	756	1,031
Total financing revenue and other interest income	2,232	2,088	4,348	4,138
Interest Expense, Deposits	399	250	750	481
Interest Expense, Short-term Borrowings	40	33	72	60
Interest Expense, Long-term Debt	434	417	845	841
Interest Expense, Related Party	0	0	0	0
Interest Expense	873	700	1,667	1,382
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	265	321	538	710
Net Financing Revenue	1,094	1,067	2,143	2,046
Dividends from Bank Subsidiary	0		0
Dividends From Non Bank Subsidiary	0	0	0	0
Insurance Services Revenue	239	227	495	468
Gain (Loss) on Sales of Loans, Net	1	36	2	50
Gain (Loss) on Investments	27	23	15	50
Noninterest Income, Other Operating Income	97	102	206	216
Nonoperating Income (Expense)	364	388	718	784
Revenues	1,458	1,455	2,861	2,830
Provision for Loan Losses Expensed	158	269	419	540
Labor and Related Expense	292	265	598	550
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	101	125	164	213
Other Noninterest Expense	446	420	891	825
Noninterest Expense	839	810	1,653	1,588
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	461	376	789	702
Income Tax Expense (Benefit)	113	122	189	235
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	348	254	600	467
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	1	(2)	(1)	(1)
Undistributed income of bank subsidiaries	0	0	0	0
Undistributed income of nonbank subsidiaries	0	0	0	0
Net Income (Loss) Attributable to Parent	349	252	599	466
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(70)	76	(398)	96
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	279	328	201	562
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	(1)	(35)	10	(70)
Interest and Fee Income, Loans and Leases Held-for-sale	0		0
Interest and Dividend Income, Securities, Operating	0	0	0	0
Interest Income, Deposits with Financial Institutions	2	2	4	4
Operating Leases, Income Statement, Lease Revenue	1	3	3	6
Total financing revenue and other interest income	8	(27)	27	(53)
Interest Expense, Deposits	0	1	0	2
Interest Expense, Short-term Borrowings	10	19	20	36
Interest Expense, Long-term Debt	257	274	515	556
Interest Expense, Related Party	4	4	7	8
Interest Expense	271	298	542	602
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	1	3	5	5
Net Financing Revenue	(264)	(328)	(520)	(660)
Dividends from Bank Subsidiary	500		1,500
Dividends From Non Bank Subsidiary	132	387	301	427
Insurance Services Revenue	0	0	0	0
Gain (Loss) on Sales of Loans, Net	0	32	28	30
Gain (Loss) on Investments	0	0	0	0
Noninterest Income, Other Operating Income	100	163	196	431
Nonoperating Income (Expense)	100	195	224	461
Revenues	468	254	1,505	228
Provision for Loan Losses Expensed	32	82	113	189
Labor and Related Expense	25	19	48	140
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	0	0	0	0
Other Noninterest Expense	173	213	355	501
Noninterest Expense	198	232	403	641
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	238	(60)	989	(602)
Income Tax Expense (Benefit)	(66)	(93)	(122)	(227)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	304	33	1,111	(375)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(1)	0	(2)	2
Undistributed income of bank subsidiaries	52	375	(545)	764
Undistributed income of nonbank subsidiaries	(6)	(156)	35	75
Net Income (Loss) Attributable to Parent	349	252	599	466
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(70)	76	(398)	96
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	279	328	201	562
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0	0	0
Interest and Fee Income, Loans and Leases Held-for-sale	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	500		1,500
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 Investments	0	0	0	0
Noninterest Income, Other Operating Income	0	0	0	0
Nonoperating Income (Expense)	0	0	0	0
Revenues	500	0	1,500	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	500	0	1,500	0
Income Tax Expense (Benefit)	0	0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	500	0	1,500	0
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0	0	0
Undistributed income of bank subsidiaries	52	375	(545)	764
Undistributed income of nonbank subsidiaries	0	0	0	0
Net Income (Loss) Attributable to Parent	552	375	955	764
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(56)	50	(332)	55
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	496	425	623	819
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	1,648	1,482	3,180	2,885
Interest and Fee Income, Loans and Leases Held-for-sale	6		6
Interest and Dividend Income, Securities, Operating	188	146	365	281
Interest Income, Deposits with Financial Institutions	14	5	28	8
Operating Leases, Income Statement, Lease Revenue	373	485	753	1,025
Total financing revenue and other interest income	2,232	2,122	4,338	4,206
Interest Expense, Deposits	395	249	750	479
Interest Expense, Short-term Borrowings	30	14	52	24
Interest Expense, Long-term Debt	177	143	330	285
Interest Expense, Related Party	8	3	10	7
Interest Expense	610	409	1,142	795
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	264	318	533	705
Net Financing Revenue	1,358	1,395	2,663	2,706
Dividends from Bank Subsidiary	0		0
Dividends From Non Bank Subsidiary	0	0	0	0
Insurance Services Revenue	239	227	495	468
Gain (Loss) on Sales of Loans, Net	1	4	2	20
Gain (Loss) on Investments	27	23	15	50
Noninterest Income, Other Operating Income	185	210	406	433
Nonoperating Income (Expense)	452	464	918	971
Revenues	1,810	1,859	3,581	3,677
Provision for Loan Losses Expensed	126	187	334	351
Labor and Related Expense	267	246	550	410
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	101	125	164	213
Other Noninterest Expense	461	478	932	972
Noninterest Expense	829	849	1,646	1,595
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	855	823	1,601	1,731
Income Tax Expense (Benefit)	179	215	311	462
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	676	608	1,290	1,269
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	2	(2)	1	(3)
Undistributed income of bank subsidiaries	0	0	0	0
Undistributed income of nonbank subsidiaries	0	0	0	0
Net Income (Loss) Attributable to Parent	678	606	1,291	1,266
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(74)	72	(413)	91
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	604	678	878	1,357
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
Gain (Loss) on Sales of Loans, Net			0	0
Affiliated Entity [Member] | Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	4	3	6	7
Interest Income, Deposits with Financial Institutions	2	0	4	0
Gain (Loss) on Sales of Loans, Net			83	1,864
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
Gain (Loss) on Sales of Loans, Net			0	0
Affiliated Entity [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	1	2	2	4
Interest Income, Deposits with Financial Institutions	2	2	4	3
Gain (Loss) on Sales of Loans, Net			(5)	246
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0	0	0
Interest and Fee Income, Loans and Leases Held-for-sale	0		0
Interest and Dividend Income, Securities, Operating	0	0	(1)	(1)
Interest Income, Deposits with Financial Institutions	1	0	0	0
Operating Leases, Income Statement, Lease Revenue	0	0	0	0
Total financing revenue and other interest income	(8)	(7)	(17)	(15)
Interest Expense, Deposits	4	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	(12)	(7)	(17)	(15)
Interest Expense	(8)	(7)	(17)	(15)
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	(1,000)		(3,000)
Dividends From Non Bank Subsidiary	(132)	(387)	(301)	(427)
Insurance Services Revenue	0	0	0	0
Gain (Loss) on Sales of Loans, Net	0	0	(28)	0
Gain (Loss) on Investments	0	0	0	0
Noninterest Income, Other Operating Income	(188)	(271)	(396)	(648)
Nonoperating Income (Expense)	(188)	(271)	(424)	(648)
Revenues	(1,320)	(658)	(3,725)	(1,075)
Provision for Loan Losses Expensed	0	0	(28)	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	(188)	(271)	(396)	(648)
Noninterest Expense	(188)	(271)	(396)	(648)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(1,132)	(387)	(3,301)	(427)
Income Tax Expense (Benefit)	0	0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(1,132)	(387)	(3,301)	(427)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0	0	0
Undistributed income of bank subsidiaries	(104)	(750)	1,090	(1,528)
Undistributed income of nonbank subsidiaries	6	156	(35)	(75)
Net Income (Loss) Attributable to Parent	(1,230)	(981)	(2,246)	(2,030)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	130	(122)	745	(146)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(1,100)	(1,103)	(1,501)	(2,176)
Consolidation, Eliminations [Member] | Affiliated Entity [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	(5)	(5)	(8)	(11)
Interest Income, Deposits with Financial Institutions	$ (4)	$ (2)	(8)	(3)
Gain (Loss) on Sales of Loans, Net			$ (78)	$ (2,110)

Parent and Guarantor Condens114

Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	$ 799			$ 844
Interest-bearing Deposits in Banks and Other Financial Institutions	3,125			3,408
Cash and Cash Equivalents, at Carrying Value	3,924			4,252	$ 4,377
Equity Securities	521			518
Available-for-sale securities	23,296			22,303
Held-to-maturity securities	2,089			1,899
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	328			108
Loans and Leases Receivable, Gross	125,544			122,893	120,528
Loans to nonbank subsidiary	0			0
Financing Receivable, Allowance for Credit Losses	1,257	$ 1,278		1,276	1,225	$ 1,155	$ 1,144
Loans and Leases Receivable, Net Amount	124,287			121,617
Property Subject to or Available for Operating Lease, Net	8,639			8,741
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	2,247			2,047
Other Assets	6,014			5,663
Assets	171,345			167,148	164,345
Noninterest-bearing deposit liabilities	153			108
Interest-bearing Deposit Liabilities	98,581			93,148
Deposits	98,734			93,256
Short-term Debt	7,108			11,413
Long-term Debt	47,328			44,226
Debt Payable To Bank Subsidiaries	0			0
Debt Payable To Nonbank Subsidiaries	0			0
Payables to Bank Subsidiaries				0
Payables to Nonbank Subsidiaries	0			0
Interest payable	568			375
Unearned Premiums	2,957			2,604
Accounts Payable and Accrued Liabilities	1,511			1,780
Liabilities	158,206			153,654
Stockholders' Equity Attributable to Parent	13,139		$ 13,375	13,494	13,473		$ 13,317
Liabilities and Equity	171,345			167,148
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	49			74
Interest-bearing Deposits in Banks and Other Financial Institutions	6			5
Cash and Cash Equivalents, at Carrying Value	1,071			1,217	1,441
Equity Securities	0			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			0
Loans and Leases Receivable, Gross	5,647			7,434
Loans to nonbank subsidiary	786			879
Financing Receivable, Allowance for Credit Losses	128			185
Loans and Leases Receivable, Net Amount	6,305			8,128
Property Subject to or Available for Operating Lease, Net	10			19
Receivables from bank subsidiary	106			80
Receivables from nonbank subsidiary	61			71
Investment in bank subsidiaries	16,163			16,962
Investment in nonbank subsidiaries	7,162			8,111
Premiums receivable and other insurance assets	0			0
Other Assets	2,123			2,207
Assets	33,001			36,795
Noninterest-bearing deposit liabilities	0			0
Interest-bearing Deposit Liabilities	6			12
Deposits	6			12
Short-term Debt	2,666			3,171
Long-term Debt	15,571			17,966
Debt Payable To Bank Subsidiaries	57			74
Debt Payable To Nonbank Subsidiaries	973			1,103
Payables to Bank Subsidiaries				4
Payables to Nonbank Subsidiaries	130			132
Interest payable	192			200
Unearned Premiums	0			0
Accounts Payable and Accrued Liabilities	267			639
Liabilities	19,862			23,301
Stockholders' Equity Attributable to Parent	13,139			13,494
Liabilities and Equity	33,001			36,795
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
Equity Securities	0			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			0
Loans and Leases Receivable, Gross	0			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	16,163			16,962
Investment in nonbank subsidiaries	0			0
Premiums receivable and other insurance assets	0			0
Other Assets	0			0
Assets	16,163			16,962
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 Bank Subsidiaries				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	16,163			16,962
Liabilities and Equity	16,163			16,962
Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	750			770
Interest-bearing Deposits in Banks and Other Financial Institutions	3,119			3,403
Cash and Cash Equivalents, at Carrying Value	4,438			4,868	3,493
Equity Securities	521			518
Available-for-sale securities	23,296			22,303
Held-to-maturity securities	2,146			1,973
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	328			108
Loans and Leases Receivable, Gross	119,897			115,459
Loans to nonbank subsidiary	405			408
Financing Receivable, Allowance for Credit Losses	1,129			1,091
Loans and Leases Receivable, Net Amount	119,173			114,776
Property Subject to or Available for Operating Lease, Net	8,629			8,722
Receivables from bank subsidiary	0			0
Receivables from nonbank subsidiary	88			77
Investment in bank subsidiaries	0			0
Investment in nonbank subsidiaries	0			0
Premiums receivable and other insurance assets	2,247			2,082
Other Assets	5,129			5,105
Assets	165,995			160,532
Noninterest-bearing deposit liabilities	153			108
Interest-bearing Deposit Liabilities	98,575			93,136
Deposits	99,744			94,383
Short-term Debt	4,442			8,242
Long-term Debt	31,757			26,260
Debt Payable To Bank Subsidiaries	0			0
Debt Payable To Nonbank Subsidiaries	786			879
Payables to Bank Subsidiaries				0
Payables to Nonbank Subsidiaries	129			127
Interest payable	376			175
Unearned Premiums	2,957			2,604
Accounts Payable and Accrued Liabilities	2,479			2,790
Liabilities	142,670			135,460
Stockholders' Equity Attributable to Parent	23,325			25,072
Liabilities and Equity	165,995			160,532
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			0
Affiliated Entity [Member] | Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	1,016			1,138
Interest-bearing Deposit Liabilities	0			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			0
Affiliated Entity [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	569			695
Interest-bearing Deposit Liabilities	1,016			1,139
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	(1,585)			(1,833)	$ (557)
Equity Securities	0			0
Available-for-sale securities	0			0
Held-to-maturity securities	(57)			(74)
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0			0
Loans and Leases Receivable, Gross	0			0
Loans to nonbank subsidiary	(1,191)			(1,287)
Financing Receivable, Allowance for Credit Losses	0			0
Loans and Leases Receivable, Net Amount	(1,191)			(1,287)
Property Subject to or Available for Operating Lease, Net	0			0
Receivables from bank subsidiary	(106)			(80)
Receivables from nonbank subsidiary	(149)			(148)
Investment in bank subsidiaries	(32,326)			(33,924)
Investment in nonbank subsidiaries	(7,162)			(8,111)
Premiums receivable and other insurance assets	0			(35)
Other Assets	(1,238)			(1,649)
Assets	(43,814)			(47,141)
Noninterest-bearing deposit liabilities	0			0
Interest-bearing Deposit Liabilities	0			0
Deposits	(1,016)			(1,139)
Short-term Debt	0			0
Long-term Debt	0			0
Debt Payable To Bank Subsidiaries	(57)			(74)
Debt Payable To Nonbank Subsidiaries	(1,759)			(1,982)
Payables to Bank Subsidiaries				(4)
Payables to Nonbank Subsidiaries	(259)			(259)
Interest payable	0			0
Unearned Premiums	0			0
Accounts Payable and Accrued Liabilities	(1,235)			(1,649)
Liabilities	(4,326)			(5,107)
Stockholders' Equity Attributable to Parent	(39,488)			(42,034)
Liabilities and Equity	(43,814)			(47,141)
Consolidation, Eliminations [Member] | Affiliated Entity [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	(1,585)			(1,833)
Interest-bearing Deposit Liabilities	$ (1,016)			$ (1,139)

Parent and Guarantor Condens115

Parent and Guarantor Condensed Consolidating Financial Statements (Statement of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities			$ 2,009	$ 2,070
Purchases of Equity Securities			(500)	(363)
Proceeds from Sales of Equity Securities			535	484
Payments to Acquire Available-for-sale Securities			(4,094)	(5,490)
Proceeds from Sale of Available-for-sale Securities			390	1,678
Proceeds from maturities and repayment of available-for-sale securities			1,621	1,230
Payments to Acquire Held-to-maturity Securities			(316)	(313)
Proceeds from Sale and Maturity of Held-to-maturity Securities			72	17
Payments to Acquire Finance Receivables			(2,611)	(1,817)
Proceeds from Sale of Loans Held-for-investment			0	1,280
Originations and repayments of loans held-for-investment and other			(638)	(1,588)
Gain (Loss) on Sales of Loans, Net	$ 1	$ 36	2	50
Purchases Of Operating Lease Assets			(2,107)	(1,965)
Disposals of Operating Lease Assets			1,763	3,043
Proceeds from Contributions from Parent			0	0
Returns Of Contributed Capital			0	0
Increase (Decrease) in Non marketable equity securities			(46)	107
Payments for (Proceeds from) Other Investing Activities			(186)	(90)
Net Cash Provided by (Used in) Investing Activities			(6,117)	(3,787)
Proceeds from (Repayments of) Short-term Debt			(4,305)	(1,962)
Increase (Decrease) in Deposit Assets			5,441	7,133
Proceeds from Issuance of Long-term Debt			12,940	9,330
Repayments of Long-term Debt			(9,800)	(14,366)
Payments for Repurchase of Common Stock			(380)	(373)
Payments of Dividends			(115)	(75)
Capital contributions from parent			0	0
Net Cash Provided by (Used in) Financing Activities			3,781	(313)
Effect of Exchange Rate on Cash and Cash Equivalents			(3)	2
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect			(330)	(2,028)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	4,939	5,853	4,939	5,853	$ 5,269	$ 7,881
Cash and Cash Equivalents, at Carrying Value	3,924	4,377	3,924	4,377	4,252
Restricted Cash	1,015	1,476	1,015	1,476
Parent Company [Member]
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities			958	561
Purchases of Equity Securities			0	0
Proceeds from Sales of Equity Securities			0	0
Payments to Acquire Available-for-sale Securities			0	0
Proceeds from Sale 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	0
Payments to Acquire Finance Receivables			0	(35)
Proceeds from Sale of Loans Held-for-investment			820	67
Originations and repayments of loans held-for-investment and other			1,331	1,044
Gain (Loss) on Sales of Loans, Net	0	32	28	30
Purchases Of Operating Lease Assets			0	0
Disposals of Operating Lease Assets			6	4
Proceeds from Contributions from Parent			(57)	(824)
Returns Of Contributed Capital			194	838
Increase (Decrease) in Non marketable equity securities			0	0
Payments for (Proceeds from) Other Investing Activities			(3)	(21)
Net Cash Provided by (Used in) Investing Activities			2,374	2,938
Proceeds from (Repayments of) Short-term Debt			(505)	1,083
Increase (Decrease) in Deposit Assets			(6)	(123)
Proceeds from Issuance of Long-term Debt			32	353
Repayments of Long-term Debt			(2,412)	(3,323)
Payments for Repurchase of Common Stock			(380)	(373)
Payments of Dividends			(115)	(75)
Capital contributions from parent			0	0
Net Cash Provided by (Used in) Financing Activities			(3,524)	(2,828)
Effect of Exchange Rate on Cash and Cash Equivalents			0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect			(192)	671
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1,203	1,660	1,203	1,660	1,395	989
Cash and Cash Equivalents, at Carrying Value	1,071	1,441	1,071	1,441	1,217
Restricted Cash	132	219	132	219
Guarantor Subsidiaries [Member]
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities			1,500	0
Purchases of Equity Securities			0	0
Proceeds from Sales of Equity Securities			0	0
Payments to Acquire Available-for-sale Securities			0	0
Proceeds from Sale 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	0
Payments to Acquire Finance Receivables			0	0
Proceeds from Sale of Loans Held-for-investment			0	0
Originations and repayments of loans held-for-investment and other			0	0
Gain (Loss) on Sales of Loans, Net	0	0	0	0
Purchases Of Operating Lease Assets			0	0
Disposals of Operating Lease Assets			0	0
Proceeds from Contributions from Parent			(6)	0
Returns Of Contributed Capital			0	0
Increase (Decrease) in Non marketable equity securities			0	0
Payments for (Proceeds from) Other Investing Activities			0	0
Net Cash Provided by (Used in) Investing Activities			(6)	0
Proceeds from (Repayments of) Short-term Debt			0	0
Increase (Decrease) in Deposit Assets			0	0
Proceeds from Issuance of Long-term Debt			0	0
Repayments of Long-term Debt			0	0
Payments for Repurchase of Common Stock			0	0
Payments of Dividends			0	0
Capital contributions from parent			6	0
Net Cash Provided by (Used in) Financing Activities			(1,494)	0
Effect of Exchange Rate on Cash and Cash Equivalents			0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect			0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	0	0	0	0	0	0
Cash and Cash Equivalents, at Carrying Value	0	0	0	0	0
Restricted Cash	0	0	0	0
Non-Guarantor Subsidiaries [Member]
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities			2,853	1,856
Purchases of Equity Securities			(500)	(363)
Proceeds from Sales of Equity Securities			535	484
Payments to Acquire Available-for-sale Securities			(4,094)	(5,490)
Proceeds from Sale of Available-for-sale Securities			390	1,678
Proceeds from maturities and repayment of available-for-sale securities			1,621	1,230
Payments to Acquire Held-to-maturity Securities			(316)	(313)
Proceeds from Sale and Maturity of Held-to-maturity Securities			72	17
Payments to Acquire Finance Receivables			(3,431)	(1,782)
Proceeds from Sale of Loans Held-for-investment			0	1,213
Originations and repayments of loans held-for-investment and other			(1,969)	(676)
Gain (Loss) on Sales of Loans, Net	1	4	2	20
Purchases Of Operating Lease Assets			(2,107)	(1,965)
Disposals of Operating Lease Assets			1,757	3,039
Proceeds from Contributions from Parent			0	0
Returns Of Contributed Capital			0	0
Increase (Decrease) in Non marketable equity securities			(46)	107
Payments for (Proceeds from) Other Investing Activities			(183)	27
Net Cash Provided by (Used in) Investing Activities			(8,259)	(2,279)
Proceeds from (Repayments of) Short-term Debt			(3,800)	(3,045)
Increase (Decrease) in Deposit Assets			5,324	7,256
Proceeds from Issuance of Long-term Debt			12,908	7,016
Repayments of Long-term Debt			(7,388)	(11,043)
Payments for Repurchase of Common Stock			0	0
Payments of Dividends			0	0
Capital contributions from parent			57	824
Net Cash Provided by (Used in) Financing Activities			5,023	(2,122)
Effect of Exchange Rate on Cash and Cash Equivalents			(3)	2
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect			(386)	(2,543)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	5,321	4,750	5,321	4,750	5,707	7,293
Cash and Cash Equivalents, at Carrying Value	4,438	3,493	4,438	3,493	4,868
Restricted Cash	883	1,257	883	1,257
Consolidation, Eliminations [Member]
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities			(3,302)	(347)
Purchases of Equity Securities			0	0
Proceeds from Sales of Equity Securities			0	0
Payments to Acquire Available-for-sale Securities			0	0
Proceeds from Sale 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	0
Payments to Acquire Finance Receivables			820	0
Proceeds from Sale of Loans Held-for-investment			(820)	0
Originations and repayments of loans held-for-investment and other			0	(1,956)
Gain (Loss) on Sales of Loans, Net	0	0	(28)	0
Purchases Of Operating Lease Assets			0	0
Disposals of Operating Lease Assets			0	0
Proceeds from Contributions from Parent			63	824
Returns Of Contributed Capital			(194)	(838)
Increase (Decrease) in Non marketable equity securities			0	0
Payments for (Proceeds from) Other Investing Activities			0	(96)
Net Cash Provided by (Used in) Investing Activities			(226)	(4,446)
Proceeds from (Repayments of) Short-term Debt			0	0
Increase (Decrease) in Deposit Assets			123	0
Proceeds from Issuance of Long-term Debt			0	1,961
Repayments of Long-term Debt			0	0
Payments for Repurchase of Common Stock			0	0
Payments of Dividends			0	0
Capital contributions from parent			(63)	(824)
Net Cash Provided by (Used in) Financing Activities			3,776	4,637
Effect of Exchange Rate on Cash and Cash Equivalents			0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect			248	(156)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	(1,585)	(557)	(1,585)	(557)	(1,833)	$ (401)
Cash and Cash Equivalents, at Carrying Value	(1,585)	(557)	(1,585)	(557)	$ (1,833)
Restricted Cash	$ 0	$ 0	0	0
Affiliated Entity [Member]
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Payments for (Proceeds from) Investments			0	0
Gain (Loss) on Sales of Loans, Net			0	0
Net Change in Debt, Intercompany			0	0
Dividends paid and returns of contributed capital, Intercompany			0	0
Affiliated Entity [Member] | Parent Company [Member]
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Payments for (Proceeds from) Investments			0	1
Gain (Loss) on Sales of Loans, Net			83	1,864
Net Change in Debt, Intercompany			(138)	(370)
Dividends paid and returns of contributed capital, Intercompany			0	0
Affiliated Entity [Member] | Guarantor Subsidiaries [Member]
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Payments for (Proceeds from) Investments			0	0
Gain (Loss) on Sales of Loans, Net			0	0
Net Change in Debt, Intercompany			0	0
Dividends paid and returns of contributed capital, Intercompany			(1,500)	0
Affiliated Entity [Member] | Non-Guarantor Subsidiaries [Member]
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Payments for (Proceeds from) Investments			17	269
Gain (Loss) on Sales of Loans, Net			(5)	246
Net Change in Debt, Intercompany			(83)	(1,864)
Dividends paid and returns of contributed capital, Intercompany			(1,995)	(1,266)
Affiliated Entity [Member] | Consolidation, Eliminations [Member]
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Payments for (Proceeds from) Investments			(17)	(270)
Gain (Loss) on Sales of Loans, Net			(78)	(2,110)
Net Change in Debt, Intercompany			221	2,234
Dividends paid and returns of contributed capital, Intercompany			$ 3,495	$ 1,266

Subsequent Events (Details)

Subsequent Events (Details) - $ / shares	Jul. 13, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Subsequent Event [Line Items]
Dividends Payable, Amount Per Share		$ 0.13	$ 0.13	$ 0.12	$ 0.12	$ 0.08	$ 0.08	$ 0.08	$ 0.08
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends Payable, Amount Per Share	$ 0.15

Uncategorized Items - ally-2018

Label	Element	Value
Treasury Stock [Member]
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	$ (1,110,000,000)
Common Stock Including Additional Paid in Capital [Member]
Stockholders' Equity Attributable to Parent	us-gaap_StockholdersEquity	21,245,000,000
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax	(250,000,000)
Accounting Standards Update 2016-01 [Member] | AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	27,000,000
Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(20,000,000)
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(126,000,000)
Accounting Standards Update 2018-02 [Member] | AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(42,000,000)
Accounting Standards Update 2018-02 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 42,000,000