Loan Receivables (Schedule of Troubled Debt Restructurings) (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Modified Credit Card Loans [Member] | Credit Card Loans [Member]    
Financing Receivable, Modifications [Line Items]    
Average recorded investment in loans $ 255 [1] $ 256 [1]
Interest income recognized during period loans were impaired 11 [1],[2] 11 [1],[2]
Gross interest income that would have been recorded with original terms 1 [1],[3] 1 [1],[3]
Internal Programs [Member] | Credit Card Loans [Member]    
Financing Receivable, Modifications [Line Items]    
Average recorded investment in loans 452 454
Interest income recognized during period loans were impaired 3 [2] 3 [2]
Gross interest income that would have been recorded with original terms 15 [3] 15 [3]
External Programs [Member] | Credit Card Loans [Member]    
Financing Receivable, Modifications [Line Items]    
Average recorded investment in loans 323 394
Interest income recognized during period loans were impaired 6 [2] 7 [2]
Gross interest income that would have been recorded with original terms 3 [3] 3 [3]
Internal And External Loan Modification Programs [Member] | Total Other Loans [Member] | Personal Loans [Member]    
Financing Receivable, Modifications [Line Items]    
Average recorded investment in loans 57 44
Interest income recognized during period loans were impaired 2 [2] 1 [2]
Gross interest income that would have been recorded with original terms 1 [3] 0 [3]
Entity Loan Modification Program [Member] | Total Other Loans [Member] | Private Student Loans [Member]    
Financing Receivable, Modifications [Line Items]    
Average recorded investment in loans 40 29
Interest income recognized during period loans were impaired $ 1 [2] $ 1 [2]
[1] This balance is considered impaired, but is excluded from the internal and external program amounts reflected in this table. Represents credit card loans that were modified in troubled debt restructurings, but are no longer enrolled in troubled debt restructuring program due to noncompliance with the terms of the modification or successful completion of a program.
[2] The Company does not separately track interest income on loans in modification programs. Amounts shown are estimated by applying an average interest rate to the average loans in the various modification programs.
[3] The Company does not separately track the amount of gross interest income that would have been recorded if the loans in modification programs had not been restructured and interest had instead been recorded in accordance with the original terms. Amounts shown are estimated by applying the difference between the average interest rate earned on non-impaired credit card loans and the average interest rate earned on loans in the modification programs to the average loans in the modification programs.