Investment Securities (Gross Unrealized Loss and Fair Value of Debt Securities ) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	$ (33)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	7,901
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(65)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	7,515
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(98)
Debt securities, available-for-sale, unrealized loss position	15,416
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
HTM unrealized loss position less than 12 months - unrealized loss	(1)
HTM unrealized loss position less than 12 months - fair value	22
HTM unrealized loss position 12 months or more - unrealized loss	(39)
HTM unrealized loss position 12 months or more - fair value	3,065
Total HTM unrealized loss	(40)
Total HTM fair value	3,087
US Treasury and Government [Member]
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(14)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	2,451
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(2)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	607
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(16)
Debt securities, available-for-sale, unrealized loss position	3,058
Residential Mortgage-backed Securities [Member] \| Mortgage-backed Securities Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(6)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	2,832
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(37)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	4,659
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(43)
Debt securities, available-for-sale, unrealized loss position	7,491
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
HTM unrealized loss position less than 12 months - unrealized loss
HTM unrealized loss position less than 12 months - fair value
HTM unrealized loss position 12 months or more - unrealized loss	(26)
HTM unrealized loss position 12 months or more - fair value	2,960
Total HTM unrealized loss	(26)
Total HTM fair value	2,960
Residential Mortgage-backed Securities [Member] \| Mortgage-backed Securities Non-agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(3)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	102
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(3)
Debt securities, available-for-sale, unrealized loss position	102
Commercial Mortgage Backed Securities [Member] \| Mortgage-backed Securities Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(6)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	852
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(12)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	953
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(18)
Debt securities, available-for-sale, unrealized loss position	1,805
Commercial Mortgage Backed Securities [Member] \| Mortgage-backed Securities Non-agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(4)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	1,106
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(5)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	230
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(9)
Debt securities, available-for-sale, unrealized loss position	1,336
Asset backed [Member]
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss	(3)
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value	660
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(5)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	561
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(8)
Debt securities, available-for-sale, unrealized loss position	1,221
Other [Member]
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months, accumulated loss
Debt securities, available-for-sale, continuous unrealized loss position, less than 12 months - fair value
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer, accumulated loss	(1)
Debt securities, available-for-sale, continuous unrealized loss position, 12 months or longer - fair value	403
Debt securities, available-for-sale, unrealized loss position, accumulated loss	(1)
Debt securities, available-for-sale, unrealized loss position	403
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
HTM unrealized loss position less than 12 months - unrealized loss	(1)
HTM unrealized loss position less than 12 months - fair value	22
HTM unrealized loss position 12 months or more - unrealized loss	(13)
HTM unrealized loss position 12 months or more - fair value	105
Total HTM unrealized loss	(14)
Total HTM fair value	$ 127

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