Available-for-Sale and Held-to-Maturity Securities (Details - Maturity) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Available-for-Sale Securities, Debt Maturities [Abstract]
Available-for-sale securities, due within one year, amortized cost	$ 0
Available-for-sale securities, due within one to five years, amortized cost	998
Available-for-sale securities, due within five to ten years, amortized cost	10,117
Available-for-sale securities, due after ten years, amortized cost	14,037
Available-for-sale debt securities, amortized cost basis	25,152
Available-for-sale securities, due within one year, fair value	0
Available-for-sale securities, due within one to five years, fair value	978
Available-for-sale securities, due within five to ten years, fair value	10,031
Available-for-sale securities, due after ten years, fair value	13,826
Available-for-sale securities, fair value	24,835
Held-to-Maturity Securities, Debt Maturities [Abstract]
Held-to-maturity securities, due within one year, amortized cost	135
Held-to-maturity securities, due within one to five years, amortized cost	1,509
Held-to-maturity securities, due within five to ten years, amortized cost	5,053
Held-to-maturity securities, due after ten years, amortized cost	13,960
Held-to-maturity securities, amortized cost	20,657	$ 23,839
Held-to-maturity securities, due within one year, fair value	135
Held-to-maturity securities, due within one to five years, fair value	1,491
Held-to-maturity securities, due within five to ten years, fair value	4,936
Held-to-maturity securities, due after ten years, fair value	13,662
Held-to-maturity securities, fair value	20,224	23,719
Available-for-Sale Securities Pledged As Collateral (Textuals) [Abstract]
Available-for-sale debt securities pledged as collateral	470	352
Held-to-Maturity Securities Pledged As Collateral (Textuals) [Abstract]
Held-to-maturity debt securities pledged as collateral	$ 4,800	$ 5,500