Loan Receivables (Schedule of Loan Receivables) (Details) (USD $)
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Total loan receivables $ 67,648,000,000 $ 69,969,000,000    
Allowance for loan losses (1,776,000,000) (1,746,000,000) (1,591,000,000) (1,648,000,000)
Net loan receivables 65,872,000,000 68,223,000,000    
Variable Interest Entity, Primary Beneficiary [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Total loan receivables 30,226,000,000 32,304,000,000    
Allowance for loan losses (826,000,000) (833,000,000)    
Credit Card Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Credit card loans 28,332,000,000 [1] 30,335,000,000 [1]    
Allowance for loan losses (798,000,000) [1] (805,000,000) [1]    
Sellers' interest 6,650,000,000 8,596,000,000    
Student Loan Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Purchased credit-impaired loans 1,894,000,000 [2] 1,969,000,000 [2]    
Allowance for loan losses (28,000,000) [2] (28,000,000) [2]    
Credit Card Loans [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Credit card loans 53,499,000,000 [3] 56,128,000,000 [3]    
Allowance for loan losses (1,492,000,000) (1,474,000,000) (1,342,000,000) (1,406,000,000)
Credit Card Loans [Member] | Credit Card Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Investors' interests 21,700,000,000 21,700,000,000    
Total Other Loans [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Total other loans 10,630,000,000 10,181,000,000    
Total Other Loans [Member] | Personal Loans [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Total other loans 5,065,000,000 5,007,000,000    
Allowance for loan losses (123,000,000) (120,000,000) (109,000,000) (112,000,000)
Total Other Loans [Member] | Private Student Loans [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Total other loans 5,177,000,000 4,850,000,000    
Total Other Loans [Member] | Mortgage Loans Held For Sale [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Total other loans 180,000,000 [4] 122,000,000 [4]    
Total Other Loans [Member] | Other Loans [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Total other loans 208,000,000 [5] 202,000,000 [5]    
Allowance for loan losses (19,000,000) [6] (17,000,000) [6] (18,000,000) (17,000,000)
Purchased Credit-Impaired Loans [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Purchased credit-impaired loans 3,519,000,000 [7] 3,660,000,000 [7]    
Allowance for loan losses (28,000,000) (28,000,000)    
Purchased Credit-Impaired Loans [Member] | Student Loan Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Loans pledged as collateral $ 1,900,000,000 $ 2,000,000,000    
[1] The Company maintains its allowance for loan losses at an amount sufficient to absorb probable losses inherent in all loan receivables, which includes all loan receivables in the trusts. Therefore, credit risk associated with the transferred receivables is fully reflected on the Company’s balance sheet in accordance with GAAP.
[2] The Company maintains its allowance for loan losses on PCI loans sufficient to absorb probable decreases in cash flows that were previously expected. Therefore, credit risk associated with the transferred receivables is fully reflected on the Company's balance sheet in accordance with GAAP.
[3] Amounts include $21.7 billion underlying investors’ interest in trust debt at March 31, 2015 and December 31, 2014 and $6.7 billion and $8.6 billion in seller's interest at March 31, 2015 and December 31, 2014, respectively. See Note 4: Credit Card and Student Loan Securitization Activities for further information.
[4] Substantially all mortgage loans held for sale are pledged as collateral against the warehouse line of credit used to fund consumer residential loans.
[5] Other includes home equity loans.
[6] Excludes mortgage loans held for sale. Certain other loans, including non-performing Diners Club licensee loans, are individually evaluated for impairment.
[7] Amounts include $1.9 billion and $2.0 billion of loans pledged as collateral against the notes issued from the Student Loan Corporation ("SLC") securitization trusts at March 31, 2015 and December 31, 2014, respectively. See Note 4: Credit Card and Student Loan Securitization Activities.