Fair Value (Fair Value of Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	$ 2,003us-gaap_LoansReceivableHeldForSaleNet	$ 35us-gaap_LoansReceivableHeldForSaleNet
Total finance receivables and loans, net	98,971	99,120
Nonmarketable equity securities	271ally_NonMarketableEquitySecurities	337ally_NonMarketableEquitySecurities
Deposit liabilities	58,222us-gaap_Deposits	53,350us-gaap_Deposits
Short-term borrowings	7,062us-gaap_ShortTermBorrowings	8,545us-gaap_ShortTermBorrowings
Long-term debt	66,558us-gaap_LongTermDebt	69,465us-gaap_LongTermDebt
Deferred interest for zero coupon bonds		359ally_DeferredInterestForZeroCouponBonds
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	2,003	35
Total finance receivables and loans, net	98,971	99,120
Nonmarketable equity securities	271	337
Deposit liabilities	58,222	53,350
Short-term borrowings	7,062	8,545
Long-term debt	66,558	69,824
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	2,039	35
Total finance receivables and loans, net	99,430	100,090
Nonmarketable equity securities	279	346
Deposit liabilities	58,777	54,070
Short-term borrowings	7,063	8,545
Long-term debt	69,308	73,364
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	0	0
Total finance receivables and loans, net	0	0
Nonmarketable equity securities	0	0
Deposit liabilities	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	485	17
Total finance receivables and loans, net	0	0
Nonmarketable equity securities	246	308
Deposit liabilities	0	0
Short-term borrowings	0	0
Long-term debt	25,224	31,067
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held-for-sale, net	1,554	18
Total finance receivables and loans, net	99,430	100,090
Nonmarketable equity securities	33	38
Deposit liabilities	58,777	54,070
Short-term borrowings	7,063	8,545
Long-term debt	$ 44,084	$ 42,297

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Nonmarketable equity securities

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- Definition

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

+ References

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- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Amount classified as loans attributable to disposal group held for sale or disposed of. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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