Investment Securities (Gross Unrealized Loss and Fair Value of Securities Available for Sale) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
AFS unrealized loss position less than 12 months - unrealized loss	$ (33)
AFS unrealized loss position less than 12 months - fair value	7,901
AFS unrealized loss position 12 months or more - unrealized loss	(65)
AFS unrealized loss position 12 months or more - fair value	7,515
Total AFS unrealized loss	(98)
Total AFS fair Value	15,416
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
U.S. Treasury and government agencies
Debt Securities, Available-for-sale [Line Items]
AFS unrealized loss position less than 12 months - unrealized loss	(14)
AFS unrealized loss position less than 12 months - fair value	2,451
AFS unrealized loss position 12 months or more - unrealized loss	(2)
AFS unrealized loss position 12 months or more - fair value	607
Total AFS unrealized loss	(16)
Total AFS fair Value	3,058
Asset-backed
Debt Securities, Available-for-sale [Line Items]
AFS unrealized loss position less than 12 months - unrealized loss	(3)
AFS unrealized loss position less than 12 months - fair value	660
AFS unrealized loss position 12 months or more - unrealized loss	(5)
AFS unrealized loss position 12 months or more - fair value	561
Total AFS unrealized loss	(8)
Total AFS fair Value	1,221
Other debt
Debt Securities, Available-for-sale [Line Items]
AFS unrealized loss position less than 12 months - unrealized loss
AFS unrealized loss position less than 12 months - fair value
AFS unrealized loss position 12 months or more - unrealized loss	(1)
AFS unrealized loss position 12 months or more - fair value	403
Total AFS unrealized loss	(1)
Total AFS fair Value	403
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
Mortgage-backed Securities Agency | Residential mortgage-backed Securities
Debt Securities, Available-for-sale [Line Items]
AFS unrealized loss position less than 12 months - unrealized loss	(6)
AFS unrealized loss position less than 12 months - fair value	2,832
AFS unrealized loss position 12 months or more - unrealized loss	(37)
AFS unrealized loss position 12 months or more - fair value	4,659
Total AFS unrealized loss	(43)
Total AFS fair Value	7,491
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
Mortgage-backed Securities Agency | Commercial Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
AFS unrealized loss position less than 12 months - unrealized loss	(6)
AFS unrealized loss position less than 12 months - fair value	852
AFS unrealized loss position 12 months or more - unrealized loss	(12)
AFS unrealized loss position 12 months or more - fair value	953
Total AFS unrealized loss	(18)
Total AFS fair Value	1,805
Mortgage-backed Securities Non-agency | Residential mortgage-backed Securities
Debt Securities, Available-for-sale [Line Items]
AFS unrealized loss position less than 12 months - unrealized loss
AFS unrealized loss position less than 12 months - fair value
AFS unrealized loss position 12 months or more - unrealized loss	(3)
AFS unrealized loss position 12 months or more - fair value	102
Total AFS unrealized loss	(3)
Total AFS fair Value	102
Mortgage-backed Securities Non-agency | Commercial Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
AFS unrealized loss position less than 12 months - unrealized loss	(4)
AFS unrealized loss position less than 12 months - fair value	1,106
AFS unrealized loss position 12 months or more - unrealized loss	(5)
AFS unrealized loss position 12 months or more - fair value	230
Total AFS unrealized loss	(9)
Total AFS fair Value	$ 1,336