Share-based Compensation Plans (Notes)	9 Months Ended
Sep. 30, 2014
Share-based Compensation Plans [Abstract]
Compensation and Employee Benefit Plans [Text Block]	Share-based Compensation Plans Based on our transactions with Treasury during 2009, we are required to comply with certain limitations on executive pay as determined by the Special Master of TARP Compensation (Special Master). We have established stock salary, or Deferred Stock Units (DSUs), and TARP Stock, or Incentive Restricted Stock Units (IRSUs), as forms of compensation to our senior executives, which have been approved by the Special Master. We also granted Restricted Stock Units (RSUs) to executives under the Long-Term Equity Compensation Incentive Plan (LTIP), and have adopted the Ally Financial 2014 Incentive Compensation Plan, which allows us to grant an array of equity-based and cash incentive awards to our named executive officers and other employees and service providers (other than our non-employee directors). Each of our approved compensation plans and awards were designed to provide our executives with an opportunity to share in the future growth in value of Ally, which is necessary to attract and retain key executives. Prior to our initial public offering (IPO) in April 2014, all share-based awards were settled in cash and required liability treatment under the accounting guidance. Accounting treatment for liability-classified awards requires compensation expense to be adjusted each period until the awards are settled based on the value of the underlying share price. Pursuant to the terms of the LTIP, the Ally Board of Directors is required to determine a share price valuation (Share Price Valuation) for share-based compensation awards not less than annually. The Share Price Valuation determined by the Board prior to the IPO, assisted by an independent advisor, considered, among other things, the stock price performance, on an indexed basis, of publicly traded common stock issued by certain comparative companies and considered Ally’s common stock as if it were freely tradable in the public markets. After the IPO, the share price valuation is based on the trading price for our stock. Also, after the IPO, certain awards, both existing and future grants, will be settled in stock and, as a result, will be accounted for as equity awards under the accounting guidance. For equity-classified awards, the compensation expense to be recognized over the vesting and service period is determined on the grant date. Certain awards will continue to require liability treatment and receive the same treatment as previously noted. For valuation purposes, we utilize Ally’s share price as of the grant date and the end of each reporting period for determining the necessary share-based compensation expense, depending on the classification of the awards. The per-share fair value based on market price for purposes of share-based compensation was $23.14 as of September 30, 2014. During the three months ended September 30, 2014, we entered into prepaid equity forward contracts to economically hedge a portion of the price risk driven by fluctuations in the fair value of our DSU and IRSU awards. The prepaid equity forward contracts are hybrid instruments containing an embedded forward contract, which is considered a derivative instrument. The embedded derivative instrument is bifurcated from the host contract and is recorded at fair value with changes in fair value recorded as compensation and benefits expense in our Condensed Consolidated Statement of Comprehensive Income. For further information on our derivative instruments, refer to Note 19. RSU Awards RSU awards are incentive awards that have been granted to employees as phantom shares of Ally. Prior to our IPO, these awards were paid in cash. As a result, RSU awards required liability treatment and were remeasured quarterly at the Share Price Valuation until they were paid. The compensation costs related to these awards were ratably charged to expense over the applicable service period. Changes in the value related to the portion of the awards that had vested and had not been paid were recognized in earnings in the period in which the changes occurred. After the IPO, the majority of existing RSU awards will settle in the form of Ally common stock, which changed the award classification from a liability award to an equity award. As a result of this classification change, a modification to the accounting for the existing awards was required. As part of the modification, the stock closing price on the date of the IPO (April 10, 2014) of $23.98 was used as the modification date value, which resulted in the recording of an increase to additional paid-in capital of $62 million, with a corresponding decrease in the liability. The remaining RSU cost for these awards, based on the modification date value, will be ratably charged to expense over the applicable service periods with an offset to additional paid-in capital. RSU awards granted in 2011 and 2012 can vest in one of two different methods. The first method allows vesting ratably over a three-year period starting on the date the award was issued, with awards fully vesting in February 2014 and February 2015. The second method allows vesting ratably over a two-year period, starting on the date the award was issued, with awards fully vesting in February 2013 and February 2014. RSU awards granted in 2013 and 2014 vest using a single method where vesting is ratable over a two-year period starting on the date the award was issued, with the majority of the awards fully vesting in January 2015 and January 2016. At September 30, 2014, there were a total of approximately 4 million award shares outstanding. We recognized expense related to RSU awards of $9 million and $35 million for the three months and nine months ended September 30, 2014, respectively. These costs were recorded as compensation and benefits expense in our Condensed Consolidated Statement of Comprehensive Income. DSU Awards DSU awards are granted to senior executives as phantom shares of Ally and are included as part of their base salary. DSU awards are generally granted ratably each pay period throughout the year, vest immediately upon grant, and are paid in cash. DSUs awarded in 2012, 2013 and 2014 will generally be redeemable in three equal installments: the first on the final payroll date of the respective year of grant, the second ratably over the first year following the grant date, and the third ratably over the second year following the grant date. The DSU awards require liability treatment and are remeasured monthly at fair value based on market price until they are paid, with each change in value fully charged to compensation expense in the period in which the change occurs. At September 30, 2014, there were a total of approximately 3 million DSU award shares outstanding. We recognized expense related to DSU awards of $11 million and $27 million for the three months and nine months ended September 30, 2014, respectively, for the outstanding awards, recorded as compensation and benefits expense in our Condensed Consolidated Statement of Comprehensive Income. IRSU Awards IRSU awards are incentive awards that have been granted to senior executives as phantom shares of Ally and vest based on continued service with Ally. IRSU awards from 2009 and 2010 have fully vested. The majority of IRSU awards from 2011 are also fully vested, with any remaining awards scheduled to vest by the end of 2014. There were no IRSU awards granted to senior executives in 2012. IRSU awards from 2013 vest two-thirds after two years from grant date and in full three years from grant date. After the vesting requirement is met, IRSU awards are paid in cash, and payouts are made only as we repay our TARP obligations. Payouts are allowed in 25% increments based on the percentage of TARP obligations that have been repaid, as determined in accordance with the established guidelines for determining "repayment." As of September 30, 2014, Ally had repaid 75% of its TARP obligations. Payouts are based on fair value of Ally shares at the time of the payout. The awards require liability treatment and are remeasured monthly at fair value based on market price until they are paid. The compensation costs related to these awards are ratably charged to expense over the requisite service period. Changes in value relating to the portion of the awards that have vested and have not been paid are recognized in earnings in the period in which the changes occur. At September 30, 2014, there were a total of approximately 1 million IRSU award shares outstanding. We recognized an immaterial amount of expense related to IRSU awards for the three months ended September 30, 2014, and a reduction of expense related to IRSU awards of $3 million for the nine months ended September 30, 2014, for the outstanding awards, recorded as compensation and benefits expense in our Condensed Consolidated Statement of Comprehensive Income.

Share-based Compensation Plans

Based on our transactions with Treasury during 2009, we are required to comply with certain limitations on executive pay as determined by the Special Master of TARP Compensation (Special Master). We have established stock salary, or Deferred Stock Units (DSUs), and TARP Stock, or Incentive Restricted Stock Units (IRSUs), as forms of compensation to our senior executives, which have been approved by the Special Master. We also granted Restricted Stock Units (RSUs) to executives under the Long-Term Equity Compensation Incentive Plan (LTIP), and have adopted the Ally Financial 2014 Incentive Compensation Plan, which allows us to grant an array of equity-based and cash incentive awards to our named executive officers and other employees and service providers (other than our non-employee directors). Each of our approved compensation plans and awards were designed to provide our executives with an opportunity to share in the future growth in value of Ally, which is necessary to attract and retain key executives.

Prior to our initial public offering (IPO) in April 2014, all share-based awards were settled in cash and required liability treatment under the accounting guidance. Accounting treatment for liability-classified awards requires compensation expense to be adjusted each period until the awards are settled based on the value of the underlying share price. Pursuant to the terms of the LTIP, the Ally Board of Directors is required to determine a share price valuation (Share Price Valuation) for share-based compensation awards not less than annually. The Share Price Valuation determined by the Board prior to the IPO, assisted by an independent advisor, considered, among other things, the stock price performance, on an indexed basis, of publicly traded common stock issued by certain comparative companies and considered Ally’s common stock as if it were freely tradable in the public markets. After the IPO, the share price valuation is based on the trading price for our stock. Also, after the IPO, certain awards, both existing and future grants, will be settled in stock and, as a result, will be accounted for as equity awards under the accounting guidance. For equity-classified awards, the compensation expense to be recognized over the vesting and service period is determined on the grant date. Certain awards will continue to require liability treatment and receive the same treatment as previously noted. For valuation purposes, we utilize Ally’s share price as of the grant date and the end of each reporting period for determining the necessary share-based compensation expense, depending on the classification of the awards. The per-share fair value based on market price for purposes of share-based compensation was $23.14 as of September 30, 2014.

During the three months ended September 30, 2014, we entered into prepaid equity forward contracts to economically hedge a portion of the price risk driven by fluctuations in the fair value of our DSU and IRSU awards. The prepaid equity forward contracts are hybrid instruments containing an embedded forward contract, which is considered a derivative instrument. The embedded derivative instrument is bifurcated from the host contract and is recorded at fair value with changes in fair value recorded as compensation and benefits expense in our Condensed Consolidated Statement of Comprehensive Income. For further information on our derivative instruments, refer to Note 19.

RSU Awards

RSU awards are incentive awards that have been granted to employees as phantom shares of Ally. Prior to our IPO, these awards were paid in cash. As a result, RSU awards required liability treatment and were remeasured quarterly at the Share Price Valuation until they were paid. The compensation costs related to these awards were ratably charged to expense over the applicable service period. Changes in the value related to the portion of the awards that had vested and had not been paid were recognized in earnings in the period in which the changes occurred. After the IPO, the majority of existing RSU awards will settle in the form of Ally common stock, which changed the award classification from a liability award to an equity award. As a result of this classification change, a modification to the accounting for the existing awards was required. As part of the modification, the stock closing price on the date of the IPO (April 10, 2014) of $23.98 was used as the modification date value, which resulted in the recording of an increase to additional paid-in capital of $62 million, with a corresponding decrease in the liability. The remaining RSU cost for these awards, based on the modification date value, will be ratably charged to expense over the applicable service periods with an offset to additional paid-in capital. RSU awards granted in 2011 and 2012 can vest in one of two different methods. The first method allows vesting ratably over a three-year period starting on the date the award was issued, with awards fully vesting in February 2014 and February 2015. The second method allows vesting ratably over a two-year period, starting on the date the award was issued, with awards fully vesting in February 2013 and February 2014. RSU awards granted in 2013 and 2014 vest using a single method where vesting is ratable over a two-year period starting on the date the award was issued, with the majority of the awards fully vesting in January 2015 and January 2016. At September 30, 2014, there were a total of approximately 4 million award shares outstanding. We recognized expense related to RSU awards of $9 million and $35 million for the three months and nine months ended September 30, 2014, respectively. These costs were recorded as compensation and benefits expense in our Condensed Consolidated Statement of Comprehensive Income.

DSU Awards

DSU awards are granted to senior executives as phantom shares of Ally and are included as part of their base salary. DSU awards are generally granted ratably each pay period throughout the year, vest immediately upon grant, and are paid in cash. DSUs awarded in 2012, 2013 and 2014 will generally be redeemable in three equal installments: the first on the final payroll date of the respective year of grant, the second ratably over the first year following the grant date, and the third ratably over the second year following the grant date. The DSU awards require liability treatment and are remeasured monthly at fair value based on market price until they are paid, with each change in value fully charged to compensation expense in the period in which the change occurs. At September 30, 2014, there were a total of approximately 3 million DSU award shares outstanding. We recognized expense related to DSU awards of $11 million and $27 million for the three months and nine months ended September 30, 2014, respectively, for the outstanding awards, recorded as compensation and benefits expense in our Condensed Consolidated Statement of Comprehensive Income.

IRSU Awards

IRSU awards are incentive awards that have been granted to senior executives as phantom shares of Ally and vest based on continued service with Ally. IRSU awards from 2009 and 2010 have fully vested. The majority of IRSU awards from 2011 are also fully vested, with any remaining awards scheduled to vest by the end of 2014. There were no IRSU awards granted to senior executives in 2012. IRSU awards from 2013 vest two-thirds after two years from grant date and in full three years from grant date. After the vesting requirement is met, IRSU awards are paid in cash, and payouts are made only as we repay our TARP obligations. Payouts are allowed in 25% increments based on the percentage of TARP obligations that have been repaid, as determined in accordance with the established guidelines for determining "repayment." As of September 30, 2014, Ally had repaid 75% of its TARP obligations. Payouts are based on fair value of Ally shares at the time of the payout. The awards require liability treatment and are remeasured monthly at fair value based on market price until they are paid. The compensation costs related to these awards are ratably charged to expense over the requisite service period. Changes in value relating to the portion of the awards that have vested and have not been paid are recognized in earnings in the period in which the changes occur. At September 30, 2014, there were a total of approximately 1 million IRSU award shares outstanding. We recognized an immaterial amount of expense related to IRSU awards for the three months ended September 30, 2014, and a reduction of expense related to IRSU awards of $3 million for the nine months ended September 30, 2014, for the outstanding awards, recorded as compensation and benefits expense in our Condensed Consolidated Statement of Comprehensive Income.