Investments (Schedule of Maturities of Available-for-Sale Debt Securities and Held-to-Maturity Debt Securities) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Investment Holdings [Line Items]    
Available-for-sale investment securities, debt maturities, one year or less, amortized cost $ 225  
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost 995  
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost 465  
Available-for-sale investment securities, debt maturities, after ten years, amortized cost 941  
Available-for-sale investment securities, amortized cost 2,626 [1] 3,811 [1]
Held-to-maturity investment securities, debt maturities, one year or less, amortized cost 1  
Held-to-maturity investment securities, debt maturities, after one year through five years, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after five years through ten years, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after ten years, amortized cost 114  
Held-to-maturity investment securities, amortized cost 115 [2] 102 [2]
Available-for-sale investment securities, debt maturities, one year or less, fair value 227  
Available-for-sale investment securities, debt maturities, after one year through five years, fair value 1,008  
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value 471  
Available-for-sale investment securities, debt maturities, after ten years, fair value 957  
Available-for-sale investment securities, fair value 2,663 [1] 3,847 [1]
Held-to-maturity investment securities, debt maturities, one year or less, fair value 1  
Held-to-maturity investment securities, debt maturities, after one year through five years, fair value 0  
Held-to-maturity investment securities, debt maturities, after five years through ten years, fair value 0  
Held-to-maturity investment securities, debt maturities, after ten years, fair value 116  
Held-to-maturity investment securities, fair value 117 [2] 104 [2]
U.S. Treasury Securities [Member]    
Investment Holdings [Line Items]    
Available-for-sale investment securities, debt maturities, one year or less, amortized cost 100  
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost 500  
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost 0  
Available-for-sale investment securities, debt maturities, after ten years, amortized cost 0  
Available-for-sale investment securities, amortized cost 600 [1] 1,317 [1]
Held-to-maturity investment securities, debt maturities, one year or less, amortized cost 1  
Held-to-maturity investment securities, debt maturities, after one year through five years, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after five years through ten years, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after ten years, amortized cost 0  
Held-to-maturity investment securities, amortized cost 1 [2],[3] 1 [2],[3]
Available-for-sale investment securities, debt maturities, one year or less, fair value 101  
Available-for-sale investment securities, debt maturities, after one year through five years, fair value 506  
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value 0  
Available-for-sale investment securities, debt maturities, after ten years, fair value 0  
Available-for-sale investment securities, fair value 607 [1] 1,329 [1]
Held-to-maturity investment securities, debt maturities, one year or less, fair value 1  
Held-to-maturity investment securities, debt maturities, after one year through five years, fair value 0  
Held-to-maturity investment securities, debt maturities, after five years through ten years, fair value 0  
Held-to-maturity investment securities, debt maturities, after ten years, fair value 0  
Held-to-maturity investment securities, fair value 1 [2],[3] 1 [2],[3]
U.S. Government Agency Securities [Member]    
Investment Holdings [Line Items]    
Available-for-sale investment securities, debt maturities, one year or less, amortized cost 125  
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost 495  
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost 0  
Available-for-sale investment securities, debt maturities, after ten years, amortized cost 0  
Available-for-sale investment securities, amortized cost 620 [1] 1,021 [1]
Available-for-sale investment securities, debt maturities, one year or less, fair value 126  
Available-for-sale investment securities, debt maturities, after one year through five years, fair value 502  
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value 0  
Available-for-sale investment securities, debt maturities, after ten years, fair value 0  
Available-for-sale investment securities, fair value 628 [1] 1,033 [1]
Residential Mortgage-Backed Securities - Agency [Member]    
Investment Holdings [Line Items]    
Available-for-sale investment securities, debt maturities, one year or less, amortized cost 0  
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost 0  
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost 465  
Available-for-sale investment securities, debt maturities, after ten years, amortized cost 941  
Available-for-sale investment securities, amortized cost 1,406 [1] 1,473 [1]
Held-to-maturity investment securities, debt maturities, one year or less, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after one year through five years, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after five years through ten years, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after ten years, amortized cost 104  
Held-to-maturity investment securities, amortized cost 104 [2],[4] 91 [2],[4]
Available-for-sale investment securities, debt maturities, one year or less, fair value 0  
Available-for-sale investment securities, debt maturities, after one year through five years, fair value 0  
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value 471  
Available-for-sale investment securities, debt maturities, after ten years, fair value 957  
Available-for-sale investment securities, fair value 1,428 [1] 1,485 [1]
Held-to-maturity investment securities, debt maturities, one year or less, fair value 0  
Held-to-maturity investment securities, debt maturities, after one year through five years, fair value 0  
Held-to-maturity investment securities, debt maturities, after five years through ten years, fair value 0  
Held-to-maturity investment securities, debt maturities, after ten years, fair value 106  
Held-to-maturity investment securities, fair value 106 [2],[4] 93 [2],[4]
States and Political Subdivisions of States [Member]    
Investment Holdings [Line Items]    
Held-to-maturity investment securities, debt maturities, one year or less, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after one year through five years, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after five years through ten years, amortized cost 0  
Held-to-maturity investment securities, debt maturities, after ten years, amortized cost 10  
Held-to-maturity investment securities, amortized cost 10 [2] 10 [2]
Held-to-maturity investment securities, debt maturities, one year or less, fair value 0  
Held-to-maturity investment securities, debt maturities, after one year through five years, fair value 0  
Held-to-maturity investment securities, debt maturities, after five years through ten years, fair value 0  
Held-to-maturity investment securities, debt maturities, after ten years, fair value 10  
Held-to-maturity investment securities, fair value $ 10 [2] $ 10 [2]
[1] Available-for-sale investment securities are reported at fair value.
[2] Held-to-maturity investment securities are reported at amortized cost.
[3] Amount represents securities pledged as collateral to a government-related merchant for which transaction settlement occurs beyond the normal 24-hour period.
[4] Amounts represent residential mortgage-backed securities that were classified as held-to-maturity as they were entered into as a part of the Company's community reinvestment initiatives.