Loans - Credit Card Portfolio - Loans Modifications (Details) (Credit card, Credit Card Loan, USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 loan_payment	Sep. 30, 2013	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	14.96%	15.26%	15.01%	15.38%
Weighted-average interest rate of loans with interest rate reductions – after TDR	4.40%	4.30%	4.37%	4.42%
Balance of loans that redefaulted within one year of permanent modification	$ 29,000,000	$ 43,000,000	$ 92,000,000	$ 128,000,000
Number of payments past due for deemed payment default			2
Rate of default for modified loans, estimated weighted average			28.31%		30.72%
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of years before payment default under a modified loan			1 year
Total new enrollments
Accounts, Notes, Loans and Financing Receivable [Line Items]
New TDRs	$ 196,000,000	$ 288,000,000	$ 622,000,000	$ 915,000,000