v3.10.0.1
Investment Securities (Investment Securities by Contractual Maturity) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Amortized Cost    
AFS debt securities: Amortized cost, total   $ 56,059
AFS equity securities: Amortized cost   15
AFS Securities: Amortized cost, total $ 62,275 56,074
HTM securities: Amortized cost, total 30,771 23,599
Investment securities: Amortized cost, total 93,046 79,673
Fair Value    
AFS debt securities: Fair value, total   55,198
AFS equity securities: Fair value   5
AFS securities: Fair value, total 61,061 55,203
HTM securities: Fair value, total 29,965 23,081
Investment securities: Fair value, total $ 91,026 78,284
Average Yield    
AFS securities: Annualized average yield, total 2.00%  
HTM securities: Annualized average yield, total 2.40%  
Investment securities: Annualized average yield, total 2.10%  
U.S. Government and Agency Securities    
Amortized Cost    
AFS debt securities: Amortized cost, total $ 57,008 49,645
HTM securities: Amortized cost, total 30,288 23,310
Fair Value    
AFS debt securities: Fair value, total 55,905 48,837
HTM securities: Fair value, total $ 29,491 22,792
Average Yield    
AFS debt securities: Annualized average yield, total 2.00%  
HTM securities: Annualized average yield, total 2.40%  
U.S. Treasury Securities    
Amortized Cost    
AFS debt securities: Amortized cost, due within 1 year $ 4,419  
AFS debt securities: Amortized cost, after 1 year through 5 years 28,607  
AFS debt securities: Amortized cost, after 5 years through 10 years 3,242  
AFS debt securities: Amortized cost, total 36,268 26,842
HTM securities: Amortized cost, due within 1 year 1,875  
HTM securities: Amortized cost, after 1 year through 5 years 7,478  
HTM securities: Amortized cost, after 5 year through 10 years 7,753  
HTM securities: Amortized cost, after 10 years 726  
HTM securities: Amortized cost, total 17,832 11,424
Fair Value    
AFS debt securities: Fair value, due within 1 year 4,387  
AFS debt securities: Fair value, after 1 year through 5 years 28,179  
AFS debt securities: Fair value, after 5 years through 10 years 3,086  
AFS debt securities: Fair value, total 35,652 26,253
HTM securities: Fair value, due within 1 year 1,870  
HTM securities: Fair value, after 1 year through 5 years 7,435  
HTM securities: Fair value, after 5 years through 10 years 7,536  
HTM securities: Fair value, after 10 years 632  
HTM securities: Fair value, total $ 17,473 11,119
Average Yield    
AFS debt securities: Annualized average yield, due within 1 year 1.60%  
AFS debt securities: Annualized average yield, after 1 year through 5 years 2.00%  
AFS debt securities: Annualized average yield, after 5 years through 10 years 1.90%  
HTM securities: Annualized average yield, due within 1 year 1.20%  
HTM securities: Annualized average yield, after 1 years through 5 years 2.30%  
HTM securities: Annualized average yield, after 5 years through 10 years 2.20%  
HTM securities: Annualized average yield, after 10 year 2.30%  
U.S. Agency Securities    
Amortized Cost    
AFS debt securities: Amortized cost, due within 1 year $ 434  
AFS debt securities: Amortized cost, after 1 year through 5 years 796  
AFS debt securities: Amortized cost, after 5 years through 10 years 1,635  
AFS debt securities: Amortized cost, after 10 years 17,875  
AFS debt securities: Amortized cost, total 20,740 22,803
HTM securities: Amortized cost, after 5 year through 10 years 30  
HTM securities: Amortized cost, after 10 years 12,426  
HTM securities: Amortized cost, total 12,456 11,886
Fair Value    
AFS debt securities: Fair value, due within 1 year 431  
AFS debt securities: Fair value, after 1 year through 5 years 784  
AFS debt securities: Fair value, after 5 years through 10 years 1,583  
AFS debt securities: Fair value, after 10 years 17,455  
AFS debt securities: Fair value, total 20,253 22,584
HTM securities: Fair value, after 5 years through 10 years 29  
HTM securities: Fair value, after 10 years 11,989  
HTM securities: Fair value, total $ 12,018 11,673
Average Yield    
AFS debt securities: Annualized average yield, due within 1 year 1.00%  
AFS debt securities: Annualized average yield, after 1 year through 5 years 1.20%  
AFS debt securities: Annualized average yield, after 5 years through 10 years 1.80%  
AFS debt securities: Annualized average yield, after 10 years 2.20%  
HTM securities: Annualized average yield, after 5 years through 10 years 1.90%  
HTM securities: Annualized average yield, after 10 year 2.70%  
Corporate and Other Debt    
Amortized Cost    
AFS debt securities: Amortized cost, total $ 5,267 6,414
Fair Value    
AFS debt securities: Fair value, total $ 5,156 6,361
Average Yield    
AFS debt securities: Annualized average yield, total 1.80%  
HTM securities: Annualized average yield, total 4.10%  
Agency CMBS    
Amortized Cost    
AFS debt securities: Amortized cost, due within 1 year $ 0  
AFS debt securities: Amortized cost, after 1 year through 5 years 283  
AFS debt securities: Amortized cost, after 5 years through 10 years 21  
AFS debt securities: Amortized cost, after 10 years 750  
AFS debt securities: Amortized cost, total 1,054 1,370
Fair Value    
AFS debt securities: Fair value, due within 1 year 0  
AFS debt securities: Fair value, after 1 year through 5 years 281  
AFS debt securities: Fair value, after 5 years through 10 years 20  
AFS debt securities: Fair value, after 10 years 691  
AFS debt securities: Fair value, total $ 992 1,323
Average Yield    
AFS debt securities: Annualized average yield, due within 1 year 0.40%  
AFS debt securities: Annualized average yield, after 1 year through 5 years 1.40%  
AFS debt securities: Annualized average yield, after 5 years through 10 years 1.20%  
AFS debt securities: Annualized average yield, after 10 years 1.60%  
Non-agency CMBS    
Amortized Cost    
AFS debt securities: Amortized cost, after 1 year through 5 years $ 36  
AFS debt securities: Amortized cost, after 5 years through 10 years 0  
AFS debt securities: Amortized cost, after 10 years 425  
AFS debt securities: Amortized cost, total 461 1,102
HTM securities: Amortized cost, due within 1 year 65  
HTM securities: Amortized cost, after 1 year through 5 years 70  
HTM securities: Amortized cost, after 5 year through 10 years 302  
HTM securities: Amortized cost, after 10 years 46  
HTM securities: Amortized cost, total 483 289
Fair Value    
AFS debt securities: Fair value, after 1 year through 5 years 34  
AFS debt securities: Fair value, after 5 years through 10 years 0  
AFS debt securities: Fair value, after 10 years 413  
AFS debt securities: Fair value, total 447 1,094
HTM securities: Fair value, due within 1 year 65  
HTM securities: Fair value, after 1 year through 5 years 69  
HTM securities: Fair value, after 5 years through 10 years 294  
HTM securities: Fair value, after 10 years 46  
HTM securities: Fair value, total $ 474 289
Average Yield    
AFS debt securities: Annualized average yield, after 1 year through 5 years 2.50%  
AFS debt securities: Annualized average yield, after 5 years through 10 years 0.00%  
AFS debt securities: Annualized average yield, after 10 years 2.40%  
HTM securities: Annualized average yield, due within 1 year 3.50%  
HTM securities: Annualized average yield, after 1 years through 5 years 4.40%  
HTM securities: Annualized average yield, after 5 years through 10 years 4.00%  
HTM securities: Annualized average yield, after 10 year 4.40%  
Corporate Bonds    
Amortized Cost    
AFS debt securities: Amortized cost, due within 1 year $ 70  
AFS debt securities: Amortized cost, after 1 year through 5 years 1,365  
AFS debt securities: Amortized cost, after 5 years through 10 years 150  
AFS debt securities: Amortized cost, total 1,585 1,379
Fair Value    
AFS debt securities: Fair value, due within 1 year 70  
AFS debt securities: Fair value, after 1 year through 5 years 1,335  
AFS debt securities: Fair value, after 5 years through 10 years 148  
AFS debt securities: Fair value, total $ 1,553 1,372
Average Yield    
AFS debt securities: Annualized average yield, due within 1 year 1.70%  
AFS debt securities: Annualized average yield, after 1 year through 5 years 2.50%  
AFS debt securities: Annualized average yield, after 5 years through 10 years 3.30%  
State and Municipal Securities    
Amortized Cost    
AFS debt securities: Amortized cost, after 1 year through 5 years $ 0  
AFS debt securities: Amortized cost, after 5 years through 10 years 200  
AFS debt securities: Amortized cost, total 200  
Fair Value    
AFS debt securities: Fair value, after 1 year through 5 years 0  
AFS debt securities: Fair value, after 5 years through 10 years 202  
AFS debt securities: Fair value, total $ 202  
Average Yield    
AFS debt securities: Annualized average yield, after 1 year through 5 years 4.80%  
AFS debt securities: Annualized average yield, after 5 years through 10 years 3.70%  
CLO    
Amortized Cost    
AFS debt securities: Amortized cost, after 5 years through 10 years $ 0  
AFS debt securities: Amortized cost, after 10 years 0  
AFS debt securities: Amortized cost, total 0 398
Fair Value    
AFS debt securities: Fair value, after 5 years through 10 years 0  
AFS debt securities: Fair value, after 10 years 0  
AFS debt securities: Fair value, total $ 0 399
Average Yield    
AFS debt securities: Annualized average yield, after 5 years through 10 years 0.00%  
AFS debt securities: Annualized average yield, after 10 years 0.00%  
FFELP Student Loan ABS    
Amortized Cost    
AFS debt securities: Amortized cost, after 1 year through 5 years $ 81  
AFS debt securities: Amortized cost, after 5 years through 10 years 307  
AFS debt securities: Amortized cost, after 10 years 1,579  
AFS debt securities: Amortized cost, total 1,967 2,165
Fair Value    
AFS debt securities: Fair value, after 1 year through 5 years 80  
AFS debt securities: Fair value, after 5 years through 10 years 303  
AFS debt securities: Fair value, after 10 years 1,579  
AFS debt securities: Fair value, total $ 1,962 $ 2,173
Average Yield    
AFS debt securities: Annualized average yield, after 1 year through 5 years 0.80%  
AFS debt securities: Annualized average yield, after 5 years through 10 years 0.80%  
AFS debt securities: Annualized average yield, after 10 years 1.20%