Investment Securities (Investment Securities in an Unrealized Loss Position) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investment securities
Investment securities: Fair Value, Less than 12 Months	$ 36,101	$ 46,712
Investment securities: Fair Value, 12 Months or Longer	32,973	19,563
Investment securities: Fair Value	69,074	66,275
Investment securities: Gross Unrealized Loss, Less than 12 Months	1,010	858
Investment securities: Gross Unrealized Loss, 12 Months or Longer	1,124	590
Investment securities: Gross Unrealized Loss	2,134	1,448
AFS Securities
AFS securities
AFS: Fair Value, Less than 12 Months	35,485	37,101
AFS: Fair Value, 12 Months or Longer	11,592	7,753
AFS: Fair Value, Total	47,077	44,854
AFS: Gross Unrealized Losses, Less than 12 Months	1,008	747
AFS: Gross Unrealized Losses, 12 Months or Longer	268	175
AFS: Gross Unrealized Losses, Total	1,276	922
AFS Debt Securities
AFS securities
AFS: Fair Value, Less than 12 Months		37,101
AFS: Fair Value, 12 Months or Longer		7,748
AFS: Fair Value, Total		44,849
AFS: Gross Unrealized Losses, Less than 12 Months		747
AFS: Gross Unrealized Losses, 12 Months or Longer		165
AFS: Gross Unrealized Losses, Total		912
AFS Debt Securities \| U.S. Government and Agency Securities
AFS securities
AFS: Fair Value, Less than 12 Months	32,841	34,614
AFS: Fair Value, 12 Months or Longer	10,136	6,800
AFS: Fair Value, Total	42,977	41,414
AFS: Gross Unrealized Losses, Less than 12 Months	924	687
AFS: Gross Unrealized Losses, 12 Months or Longer	229	149
AFS: Gross Unrealized Losses, Total	1,153	836
AFS Debt Securities \| U.S. Treasury Securities
AFS securities
AFS: Fair Value, Less than 12 Months	19,937	21,941
AFS: Fair Value, 12 Months or Longer	5,994	4,287
AFS: Fair Value, Total	25,931	26,228
AFS: Gross Unrealized Losses, Less than 12 Months	541	495
AFS: Gross Unrealized Losses, 12 Months or Longer	115	94
AFS: Gross Unrealized Losses, Total	656	589
AFS Debt Securities \| U.S. Agency Securities
AFS securities
AFS: Fair Value, Less than 12 Months	12,904	12,673
AFS: Fair Value, 12 Months or Longer	4,142	2,513
AFS: Fair Value, Total	17,046	15,186
AFS: Gross Unrealized Losses, Less than 12 Months	383	192
AFS: Gross Unrealized Losses, 12 Months or Longer	114	55
AFS: Gross Unrealized Losses, Total	497	247
AFS Debt Securities \| Corporate and Other Debt
AFS securities
AFS: Fair Value, Less than 12 Months	2,644	2,487
AFS: Fair Value, 12 Months or Longer	1,456	948
AFS: Fair Value, Total	4,100	3,435
AFS: Gross Unrealized Losses, Less than 12 Months	84	60
AFS: Gross Unrealized Losses, 12 Months or Longer	39	16
AFS: Gross Unrealized Losses, Total	123	76
AFS Debt Securities \| Agency CMBS
AFS securities
AFS: Fair Value, Less than 12 Months	808	930
AFS: Fair Value, 12 Months or Longer	0	0
AFS: Fair Value, Total	808	930
AFS: Gross Unrealized Losses, Less than 12 Months	62	49
AFS: Gross Unrealized Losses, 12 Months or Longer	0	0
AFS: Gross Unrealized Losses, Total	62	49
AFS Debt Securities \| Non-agency CMBS
AFS securities
AFS: Fair Value, Less than 12 Months	0	257
AFS: Fair Value, 12 Months or Longer	446	559
AFS: Fair Value, Total	446	816
AFS: Gross Unrealized Losses, Less than 12 Months	0	1
AFS: Gross Unrealized Losses, 12 Months or Longer	14	7
AFS: Gross Unrealized Losses, Total	14	8
AFS Debt Securities \| Corporate Bonds
AFS securities
AFS: Fair Value, Less than 12 Months	470	316
AFS: Fair Value, 12 Months or Longer	1,010	389
AFS: Fair Value, Total	1,480	705
AFS: Gross Unrealized Losses, Less than 12 Months	7	3
AFS: Gross Unrealized Losses, 12 Months or Longer	25	9
AFS: Gross Unrealized Losses, Total	32	12
AFS Debt Securities \| FFELP Student Loan ABS
AFS securities
AFS: Fair Value, Less than 12 Months	1,366	984
AFS: Fair Value, 12 Months or Longer	0	0
AFS: Fair Value, Total	1,366	984
AFS: Gross Unrealized Losses, Less than 12 Months	15	7
AFS: Gross Unrealized Losses, 12 Months or Longer	0	0
AFS: Gross Unrealized Losses, Total	15	7
AFS Equity Securities
AFS securities
AFS: Fair Value, Less than 12 Months		0
AFS: Fair Value, 12 Months or Longer		5
AFS: Fair Value, Total		5
AFS: Gross Unrealized Losses, Less than 12 Months		0
AFS: Gross Unrealized Losses, 12 Months or Longer		10
AFS: Gross Unrealized Losses, Total		10
HTM securities
HTM securities
HTM: Fair Value, Less than 12 Months	616	9,611
HTM: Fair Value, 12 Months or Longer	21,381	11,810
HTM: Fair Value, Total	21,997	21,421
HTM: Gross Unrealized Losses, Less than 12 Months	2	111
HTM: Gross Unrealized Losses, 12 Months or Longer	856	415
HTM: Gross Unrealized Losses, Total	858	526
HTM securities \| U.S. Government and Agency Securities
HTM securities
HTM: Fair Value, Less than 12 Months	410	9,487
HTM: Fair Value, 12 Months or Longer	21,165	11,810
HTM: Fair Value, Total	21,575	21,297
HTM: Gross Unrealized Losses, Less than 12 Months	1	110
HTM: Gross Unrealized Losses, 12 Months or Longer	848	415
HTM: Gross Unrealized Losses, Total	849	525
HTM securities \| U.S. Treasury Securities
HTM securities
HTM: Fair Value, Less than 12 Months	0	6,608
HTM: Fair Value, 12 Months or Longer	11,161	4,512
HTM: Fair Value, Total	11,161	11,120
HTM: Gross Unrealized Losses, Less than 12 Months	0	86
HTM: Gross Unrealized Losses, 12 Months or Longer	403	219
HTM: Gross Unrealized Losses, Total	403	305
HTM securities \| U.S. Agency Securities
HTM securities
HTM: Fair Value, Less than 12 Months	410	2,879
HTM: Fair Value, 12 Months or Longer	10,004	7,298
HTM: Fair Value, Total	10,414	10,177
HTM: Gross Unrealized Losses, Less than 12 Months	1	24
HTM: Gross Unrealized Losses, 12 Months or Longer	445	196
HTM: Gross Unrealized Losses, Total	446	220
HTM securities \| Non-agency CMBS
HTM securities
HTM: Fair Value, Less than 12 Months	206	124
HTM: Fair Value, 12 Months or Longer	216	0
HTM: Fair Value, Total	422	124
HTM: Gross Unrealized Losses, Less than 12 Months	1	1
HTM: Gross Unrealized Losses, 12 Months or Longer	8	0
HTM: Gross Unrealized Losses, Total	$ 9	$ 1

Amount of unrealized loss on investments securities that have been in a loss position for twelve months or longer.

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

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