Description Of Business, Basis Of Presentation, And Changes In Significant Accounting Policies Description Of Business, Basis of Presentation, And Changes in Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2012
Description Of Business, Basis Of Presentation, And Changes In Significant Accounting Policies [Abstract]
Nature of operations [Policy Text Block]	Ally Financial Inc. (formerly GMAC Inc. and referred to herein as Ally, we, our, or us) is a leading, independent, globally diversified, financial services firm. Founded in 1919, we are a leading automotive financial services company with over 90 years experience providing a broad array of financial products and services to automotive dealers and their customers. We became a bank holding company on December 24, 2008, under the Bank Holding Company Act of 1956, as amended. Our banking subsidiary, Ally Bank, is an indirect wholly owned subsidiary of Ally Financial Inc. and a leading franchise in the growing direct (online and telephonic) banking market.
Basis of Accounting [Policy Text Block]	Our accounting and reporting policies conform to accounting principles generally accepted in the United States of America (GAAP). Additionally, where applicable, the policies conform to the accounting and reporting guidelines prescribed by bank regulatory authorities.
Use of Estimates, Policy [Policy Text Block]	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and that affect income and expenses during the reporting period. 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.
Income Tax, Policy [Policy Text Block]	Income Taxes In calculating the provision for interim income taxes, in accordance with Accounting Standards Codification (ASC) 740, Income Taxes, we apply an estimated annual effective tax rate to year-to-date ordinary income. At the end of each interim period, we estimate the effective tax rate expected to be applicable for the full fiscal year. We exclude and record discretely the tax effect of unusual or infrequently occurring items, including, for example, changes in judgment about valuation allowances and effects of changes in tax law or rates. The provision for income taxes in tax jurisdictions with a projected full year or year-to-date loss for which a tax benefit cannot be realized are estimated using tax rates specific to that jurisdiction. Refer to Note 1 to the Consolidated Financial Statements in our 2011 Annual Report on Form 10-K regarding additional significant accounting policies.
Recently adopted accounting standards [Policy Text Block]	Recently Adopted Accounting Standards Financial Services - Insurance - Accounting for Costs Associated with Acquiring or Renewing Insurance Contracts (ASU 2010-26) As of January 1, 2012, we adopted Accounting Standards Update (ASU) 2010-26, which amends ASC 944, Financial Services - Insurance. The amendments in this ASU specify which costs incurred in the acquisition of new and renewal insurance contracts should be capitalized. All other acquisition-related costs should be expensed as incurred. If the initial application of the amendments in this ASU results in the capitalization of acquisition costs that had not been previously capitalized, an entity may elect not to capitalize those types of costs. Both retrospective application and early adoption was permitted. We elected prospective application and did not early adopt the ASU. The adoption did not have a material impact to our consolidated financial condition or results of operations. Fair Value Measurement - Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs (ASU 2011-04) As of January 1, 2012, we adopted ASU 2011-04, which amends ASC 820, Fair Value Measurements. The amendments in this ASU clarify how to measure fair value and it contains new disclosure requirements to provide more transparency into Level 3 fair value measurements. It is intended to improve the comparability of fair value measurements presented and disclosed in financial statements prepared in accordance with U.S. GAAP and International Financial Reporting Standards (IFRS). The ASU must be applied prospectively. The adoption did not have a material impact to our consolidated financial condition or results of operations. Intangibles-Goodwill and Other - Testing Goodwill for Impairment (ASU 2011-08) As of January 1, 2012, we adopted ASU 2011-08, which amends ASC 350, Intangibles-Goodwill and Other. This ASU permits the option of performing a qualitative assessment before calculating the fair value of a reporting unit in step 1 of the goodwill impairment test. If it is determined, on the basis of qualitative factors, that the fair value of a reporting unit is more likely than not more than the carrying amount, the two-step impairment test would not be required. Otherwise, further evaluation under the existing two-step framework would be required. The adoption did not have a material impact to our consolidated financial condition or results of operation.
Recently issued accounting standards [Policy Text Block]	Recently Issued Accounting Standards Balance Sheet - Disclosures about Offsetting Assets and Liabilities (ASU 2011-11) In December 2011, the Financial Accounting Standards Board issued ASU 2011-11, which amends ASC 210, Balance Sheet. This ASU contains new disclosure requirements regarding the nature of an entity's rights of setoff and related arrangements associated with its financial instruments and derivative instruments. The new disclosures will give financial statement users information about both gross and net exposures. ASU 2011-11 is effective for us on January 1, 2013, and retrospective application is required. Since the guidance relates only to disclosures, adoption is not expected to have a material effect on our consolidated financial condition or results of operations.
Discontinued Operations, Policy [Policy Text Block]	We classify operations as discontinued when operations and cash flows will be eliminated from our ongoing operations and we do not expect to retain any significant continuing involvement in their operations after the respective sale transactions. For all periods presented, all of the operating results for these discontinued operations have been removed from continuing operations and presented separately as discontinued operations, net of tax, in the Condensed Consolidated Statement of Comprehensive Income. The Notes to the Condensed Consolidated Financial Statements have been adjusted to exclude discontinued operations unless otherwise noted.
Finance, Loan and Lease Receivables, Held-for-investment, Policy [Policy Text Block]	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 2011 Annual Report on Form 10-K.
Loans and Leases Receivable, Troubled Debt Restructuring Policy [Policy Text Block]	The following tables present information about finance receivables and loans recorded at historical cost that have redefaulted during the reporting period and were within 12 months or less of being modified as a troubled debt restructuring. 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 2011 Annual Report on Form 10-K for additional information) except for commercial finance receivables and loans where default is defined as 90 days past due. TDRs are loan modifications where concessions were granted to borrowers experiencing financial difficulties. Numerous initiatives, such as the Home Affordable Modification Program (HARP) 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. Additionally for automobile loans, we offer several types of assistance to aid our customers including changing the due date and rewriting the loan terms. Total TDRs recorded at historical cost and reported at carrying value before allowance for loan losses were $829 million at June 30, 2012, reflecting an increase of $95 million from December 31, 2011. Refer to Note 1 to the Consolidated Financial Statements in our 2011 Annual Report on Form 10-K for additional information.

Description Of Business, Basis Of Presentation, And Changes In Significant Accounting Policies Description Of Business, Basis of Presentation, And Changes in Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2012

Description Of Business, Basis Of Presentation, And Changes In Significant Accounting Policies [Abstract]

Nature of operations [Policy Text Block]

Ally Financial Inc. (formerly GMAC Inc. and referred to herein as Ally, we, our, or us) is a leading, independent, globally diversified, financial services firm. Founded in 1919, we are a leading automotive financial services company with over 90 years experience providing a broad array of financial products and services to automotive dealers and their customers. We became a bank holding company on December 24, 2008, under the Bank Holding Company Act of 1956, as amended. Our banking subsidiary, Ally Bank, is an indirect wholly owned subsidiary of Ally Financial Inc. and a leading franchise in the growing direct (online and telephonic) banking market.

Basis of Accounting [Policy Text Block]

Our accounting and reporting policies conform to accounting principles generally accepted in the United States of America (GAAP). Additionally, where applicable, the policies conform to the accounting and reporting guidelines prescribed by bank regulatory authorities.

Use of Estimates, Policy [Policy Text Block]

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and that affect income and expenses during the reporting period. 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.

Income Tax, Policy [Policy Text Block]

Income Taxes

In calculating the provision for interim income taxes, in accordance with Accounting Standards Codification (ASC) 740, Income Taxes, we apply an estimated annual effective tax rate to year-to-date ordinary income. At the end of each interim period, we estimate the effective tax rate expected to be applicable for the full fiscal year. We exclude and record discretely the tax effect of unusual or infrequently occurring items, including, for example, changes in judgment about valuation allowances and effects of changes in tax law or rates. The provision for income taxes in tax jurisdictions with a projected full year or year-to-date loss for which a tax benefit cannot be realized are estimated using tax rates specific to that jurisdiction.

Refer to Note 1 to the Consolidated Financial Statements in our 2011 Annual Report on Form 10-K regarding additional significant accounting policies.

Recently adopted accounting standards [Policy Text Block]

Recently Adopted Accounting Standards

Financial Services - Insurance - Accounting for Costs Associated with Acquiring or Renewing Insurance Contracts (ASU 2010-26)

As of January 1, 2012, we adopted Accounting Standards Update (ASU) 2010-26, which amends ASC 944, Financial Services - Insurance. The amendments in this ASU specify which costs incurred in the acquisition of new and renewal insurance contracts should be capitalized. All other acquisition-related costs should be expensed as incurred. If the initial application of the amendments in this ASU results in the capitalization of acquisition costs that had not been previously capitalized, an entity may elect not to capitalize those types of costs. Both retrospective application and early adoption was permitted. We elected prospective application and did not early adopt the ASU. The adoption did not have a material impact to our consolidated financial condition or results of operations.

Fair Value Measurement - Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs (ASU 2011-04)

As of January 1, 2012, we adopted ASU 2011-04, which amends ASC 820, Fair Value Measurements. The amendments in this ASU clarify how to measure fair value and it contains new disclosure requirements to provide more transparency into Level 3 fair value measurements. It is intended to improve the comparability of fair value measurements presented and disclosed in financial statements prepared in accordance with U.S. GAAP and International Financial Reporting Standards (IFRS). The ASU must be applied prospectively. The adoption did not have a material impact to our consolidated financial condition or results of operations.

Intangibles-Goodwill and Other - Testing Goodwill for Impairment (ASU 2011-08)

As of January 1, 2012, we adopted ASU 2011-08, which amends ASC 350, Intangibles-Goodwill and Other. This ASU permits the option of performing a qualitative assessment before calculating the fair value of a reporting unit in step 1 of the goodwill impairment test. If it is determined, on the basis of qualitative factors, that the fair value of a reporting unit is more likely than not more than the carrying amount, the two-step impairment test would not be required. Otherwise, further evaluation under the existing two-step framework would be required. The adoption did not have a material impact to our consolidated financial condition or results of operation.

Recently issued accounting standards [Policy Text Block]

Recently Issued Accounting Standards

Balance Sheet - Disclosures about Offsetting Assets and Liabilities (ASU 2011-11)

In December 2011, the Financial Accounting Standards Board issued ASU 2011-11, which amends ASC 210, Balance Sheet. This ASU contains new disclosure requirements regarding the nature of an entity's rights of setoff and related arrangements associated with its financial instruments and derivative instruments. The new disclosures will give financial statement users information about both gross and net exposures. ASU 2011-11 is effective for us on January 1, 2013, and retrospective application is required. Since the guidance relates only to disclosures, adoption is not expected to have a material effect on our consolidated financial condition or results of operations.

Discontinued Operations, Policy [Policy Text Block]

We classify operations as discontinued when operations and cash flows will be eliminated from our ongoing operations and we do not expect to retain any significant continuing involvement in their operations after the respective sale transactions. For all periods presented, all of the operating results for these discontinued operations have been removed from continuing operations and presented separately as discontinued operations, net of tax, in the Condensed Consolidated Statement of Comprehensive Income. The Notes to the Condensed Consolidated Financial Statements have been adjusted to exclude discontinued operations unless otherwise noted.

Finance, Loan and Lease Receivables, Held-for-investment, Policy [Policy Text Block]

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 2011 Annual Report on Form 10-K.

Loans and Leases Receivable, Troubled Debt Restructuring Policy [Policy Text Block]

The following tables present information about finance receivables and loans recorded at historical cost that have redefaulted during the reporting period and were within 12 months or less of being modified as a troubled debt restructuring. 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 2011 Annual Report on Form 10-K for additional information) except for commercial finance receivables and loans where default is defined as 90 days past due.

TDRs are loan modifications where concessions were granted to borrowers experiencing financial difficulties. Numerous initiatives, such as the Home Affordable Modification Program (HARP) 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. Additionally for automobile loans, we offer several types of assistance to aid our customers including changing the due date and rewriting the loan terms. Total TDRs recorded at historical cost and reported at carrying value before allowance for loan losses were $829 million at June 30, 2012, reflecting an increase of $95 million from December 31, 2011. Refer to Note 1 to the Consolidated Financial Statements in our 2011 Annual Report on Form 10-K for additional information.