Investment Securities (Summary Of Investment Securities Available-For-Sale) (Details) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Investment securities available-for-sale, Amortized Cost $ 12,244 $ 11,061 [1]
Investment securities available-for-sale securities, Gross Unrealized Gains 13 23 [1]
Investment securities available-for-sale securities, Gross Unrealized Losses 286 146 [1]
Investment securities available-for-sale, Fair Value 11,971 10,938 [1]
Investment securities held-to-maturity, Amortized Cost 0 1,266
Net unrealized losses on available-for-sale securities transferred to held-to-maturity   9
U.S. Treasury and other U.S. government agency securities    
Investment securities available-for-sale, Amortized Cost 2,744 2,743
Investment securities available-for-sale securities, Gross Unrealized Gains 0 0
Investment securities available-for-sale securities, Gross Unrealized Losses 38 16
Investment securities available-for-sale, Fair Value 2,706 2,727
Residential mortgage-backed securities    
Investment securities available-for-sale, Amortized Cost [2] 9,500 8,230
Investment securities available-for-sale securities, Gross Unrealized Gains [2] 13 22
Investment securities available-for-sale securities, Gross Unrealized Losses [2] 248 128
Investment securities available-for-sale, Fair Value [2] 9,265 8,124
Investment securities held-to-maturity, Amortized Cost [2],[3]   1,266
Investment securities held-to-maturity, Gross Unrealized Gains [2],[3]   0
Investment securities held-to-maturity, Gross Unrealized Losses [2],[3]   20
Investment securities held-to-maturity, Fair Value [2],[3]   1,246
State and municipal securities    
Investment securities available-for-sale, Amortized Cost   5
Investment securities available-for-sale securities, Gross Unrealized Gains   0
Investment securities available-for-sale securities, Gross Unrealized Losses   0
Investment securities available-for-sale, Fair Value   5
Equity and other non-debt securities    
Investment securities available-for-sale, Amortized Cost   83
Investment securities available-for-sale securities, Gross Unrealized Gains   1
Investment securities available-for-sale securities, Gross Unrealized Losses   2
Investment securities available-for-sale, Fair Value   82
Auction-rate securities    
Investment securities available-for-sale, Amortized Cost 0 51
Investment securities available-for-sale, Fair Value $ 0 $ 49
[1] Included auction-rate securities at amortized cost and fair value of $51 million and $49 million, respectively, as of December 31, 2017.
[2] Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.
[3] The amortized cost of investment securities held-to-maturity included net unrealized losses of $9 million at December 31, 2017 related to securities transferred from available-for-sale in 2014, which are included in accumulated other comprehensive loss.