Quarterly report pursuant to Section 13 or 15(d)

Securities - Maturities of Debt Securities Carried at Fair Value and Held-to-maturity Debt Securities (Details)

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Securities - Maturities of Debt Securities Carried at Fair Value and Held-to-maturity Debt Securities (Details) - USD ($)
$ in Millions
Jun. 30, 2018
Dec. 31, 2017
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]    
Due in One Year or Less, Amount $ 4  
Due in One Year or Less, Yield 3.36%  
Due after One Year through Five Years, Amount $ 63  
Due after One Year through Five Years, Yield 3.56%  
Due after Five Years through Ten Years, Amount $ 1,427  
Due after Five Years though Ten Years, Yield 2.78%  
Due after Ten Years, Amount $ 161,519  
Due after Ten Years, Yield 3.15%  
Amortized Cost $ 163,013 $ 125,013
Total, Yield 3.15%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Debt securities carried at fair value $ 275,256 315,117
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]    
Due in One Year or Less, Amount 4  
Due after One Year through Five Years, Amount 63  
Due after Five Years though Ten Years, Amount 1,363  
Due after Ten Years, Amount 156,801  
Held-to-maturity Securities, Fair Value 158,231 $ 123,299
Mortgage-backed securities    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 56  
Due in One Year or Less, Yield 9.33%  
Due after One Year through Five Years, Amount $ 2,181  
Due after One Year through Five Years, Yield 2.24%  
Due after Five Years though Ten Years, Amount $ 11,596  
Due after Five Years though Ten Years, Yield 2.48%  
Due after Ten Years, Amount $ 173,382  
Due after Ten Years, Yield 3.43%  
Total, Amount $ 187,215  
Total, Yield 3.36%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 56  
Due after One Year through Five Years, Amount 2,134  
Due after Five Years though Ten Years, Amount 11,139  
Due after Ten Years, Amount 168,375  
Debt securities carried at fair value 181,704  
Agency    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 2  
Due in One Year or Less, Yield 3.50%  
Due after One Year through Five Years, Amount $ 26  
Due after One Year through Five Years, Yield 3.98%  
Due after Five Years though Ten Years, Amount $ 492  
Due after Five Years though Ten Years, Yield 2.61%  
Due after Ten Years, Amount $ 161,781  
Due after Ten Years, Yield 3.26%  
Total, Amount $ 162,301  
Total, Yield 3.26%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 2  
Due after One Year through Five Years, Amount 26  
Due after Five Years though Ten Years, Amount 484  
Due after Ten Years, Amount 156,488  
Debt securities carried at fair value 157,000  
Agency-collateralized mortgage obligations    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 0  
Due in One Year or Less, Yield 0.00%  
Due after One Year through Five Years, Amount $ 0  
Due after One Year through Five Years, Yield 0.00%  
Due after Five Years though Ten Years, Amount $ 31  
Due after Five Years though Ten Years, Yield 2.55%  
Due after Ten Years, Amount $ 6,163  
Due after Ten Years, Yield 3.17%  
Total, Amount $ 6,194  
Total, Yield 3.17%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 0  
Due after One Year through Five Years, Amount 0  
Due after Five Years though Ten Years, Amount 30  
Due after Ten Years, Amount 6,005  
Debt securities carried at fair value 6,035  
Commercial    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 54  
Due in One Year or Less, Yield 9.55%  
Due after One Year through Five Years, Amount $ 2,155  
Due after One Year through Five Years, Yield 2.22%  
Due after Five Years though Ten Years, Amount $ 11,052  
Due after Five Years though Ten Years, Yield 2.48%  
Due after Ten Years, Amount $ 895  
Due after Ten Years, Yield 2.81%  
Total, Amount $ 14,156  
Total, Yield 2.49%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 54  
Due after One Year through Five Years, Amount 2,108  
Due after Five Years though Ten Years, Amount 10,592  
Due after Ten Years, Amount 846  
Debt securities carried at fair value 13,600  
Non-agency residential    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 0  
Due in One Year or Less, Yield 0.00%  
Due after One Year through Five Years, Amount $ 0  
Due after One Year through Five Years, Yield 0.00%  
Due after Five Years though Ten Years, Amount $ 21  
Due after Five Years though Ten Years, Yield 0.01%  
Due after Ten Years, Amount $ 4,543  
Due after Ten Years, Yield 9.82%  
Total, Amount $ 4,564  
Total, Yield 9.77%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 0  
Due after One Year through Five Years, Amount 0  
Due after Five Years though Ten Years, Amount 33  
Due after Ten Years, Amount 5,036  
Debt securities carried at fair value 5,069  
U.S. Treasury and agency securities    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 542  
Due in One Year or Less, Yield 0.45%  
Due after One Year through Five Years, Amount $ 32,638  
Due after One Year through Five Years, Yield 1.47%  
Due after Five Years though Ten Years, Amount $ 21,549  
Due after Five Years though Ten Years, Yield 2.24%  
Due after Ten Years, Amount $ 29  
Due after Ten Years, Yield 2.70%  
Total, Amount $ 54,758  
Total, Yield 1.76%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 542  
Due after One Year through Five Years, Amount 31,381  
Due after Five Years though Ten Years, Amount 20,783  
Due after Ten Years, Amount 28  
Debt securities carried at fair value 52,734  
Non-U.S. securities    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 15,118  
Due in One Year or Less, Yield 0.79%  
Due after One Year through Five Years, Amount $ 1,787  
Due after One Year through Five Years, Yield 1.53%  
Due after Five Years though Ten Years, Amount $ 2  
Due after Five Years though Ten Years, Yield 3.56%  
Due after Ten Years, Amount $ 140  
Due after Ten Years, Yield 6.55%  
Total, Amount $ 17,047  
Total, Yield 0.91%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 15,121  
Due after One Year through Five Years, Amount 1,798  
Due after Five Years though Ten Years, Amount 2  
Due after Ten Years, Amount 144  
Debt securities carried at fair value 17,065  
Other taxable securities, substantially all asset-backed securities    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 576  
Due in One Year or Less, Yield 3.39%  
Due after One Year through Five Years, Amount $ 2,886  
Due after One Year through Five Years, Yield 3.34%  
Due after Five Years though Ten Years, Amount $ 874  
Due after Five Years though Ten Years, Yield 3.24%  
Due after Ten Years, Amount $ 260  
Due after Ten Years, Yield 8.56%  
Total, Amount $ 4,596  
Total, Yield 3.62%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 571  
Due after One Year through Five Years, Amount 2,905  
Due after Five Years though Ten Years, Amount 916  
Due after Ten Years, Amount 296  
Debt securities carried at fair value 4,688  
Total taxable securities    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 16,292  
Due in One Year or Less, Yield 0.90%  
Due after One Year through Five Years, Amount $ 39,492  
Due after One Year through Five Years, Yield 1.65%  
Due after Five Years though Ten Years, Amount $ 34,021  
Due after Five Years though Ten Years, Yield 2.35%  
Due after Ten Years, Amount $ 173,811  
Due after Ten Years, Yield 3.44%  
Total, Amount $ 263,616  
Total, Yield 2.87%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 16,290  
Due after One Year through Five Years, Amount 38,218  
Due after Five Years though Ten Years, Amount 32,840  
Due after Ten Years, Amount 168,843  
Debt securities carried at fair value 256,191  
Tax-exempt securities    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 894  
Due in One Year or Less, Yield 1.71%  
Due after One Year through Five Years, Amount $ 8,332  
Due after One Year through Five Years, Yield 2.27%  
Due after Five Years though Ten Years, Amount $ 7,252  
Due after Five Years though Ten Years, Yield 2.22%  
Due after Ten Years, Amount $ 2,607  
Due after Ten Years, Yield 2.64%  
Total, Amount $ 19,085  
Total, Yield 2.28%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 894  
Due after One Year through Five Years, Amount 8,347  
Due after Five Years though Ten Years, Amount 7,230  
Due after Ten Years, Amount 2,594  
Debt securities carried at fair value 19,065  
Debt securities    
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 17,186  
Due in One Year or Less, Yield 0.94%  
Due after One Year through Five Years, Amount $ 47,824  
Due after One Year through Five Years, Yield 1.76%  
Due after Five Years though Ten Years, Amount $ 41,273  
Due after Five Years though Ten Years, Yield 2.32%  
Due after Ten Years, Amount $ 176,418  
Due after Ten Years, Yield 3.42%  
Total, Amount $ 282,701  
Total, Yield 2.83%  
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]    
Due in One Year or Less, Amount $ 17,184  
Due after One Year through Five Years, Amount 46,565  
Due after Five Years though Ten Years, Amount 40,070  
Due after Ten Years, Amount 171,437  
Debt securities carried at fair value $ 275,256