Condensed Consolidated Statements of Income (USD $)
In Millions, except Per Share data, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Interest income:    
Credit card loans $ 1,606 $ 1,537
Other loans 304 275
Investment securities 13 16
Other interest income 6 5
Total interest income 1,929 1,833
Interest expense:    
Deposits 152 153
Short-term borrowings 1 1
Long-term borrowings 147 116
Total interest expense 300 270
Net interest income 1,629 1,563
Provision for loan losses 390 272
Net interest income after provision for loan losses 1,239 1,291
Other income:    
Discount and interchange revenue, net 268 254
Protection products revenue 71 83
Loan fee income 81 83
Transaction processing revenue 42 44
Gain on investments 8 4
Gain on origination and sale of mortgage loans 40 16
Other income 32 31
Total other income 542 515
Other expense:    
Employee compensation and benefits 331 307
Marketing and business development 182 169
Information processing and communications 88 84
Professional fees 127 99
Premises and equipment 24 23
Other expense 121 102
Total other expense 873 784
Income before income tax expense 908 1,022
Income tax expense 322 391
Net income 586 631
Net income allocated to common stockholders $ 573 $ 618
Basic earnings per common share (in dollars per share) $ 1.28 $ 1.31
Diluted earnings per common share (in dollars per share) $ 1.28 $ 1.31
Dividends declared per common share (in dollars per share) $ 0.24 $ 0.20