Investment Securities - Securities in Gross Unrealized Loss Position (Details) $ in Millions	Jun. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	$ 17,993	$ 30,629
Fair Value - 12 Months or Longer	56,222	40,544
Fair Value - Total	74,215	71,173
Gross Unrealized Loss - Less than 12 Months	(550)	(2,141)
Gross Unrealized Loss - 12 Months or Longer	(9,618)	(8,133)
Gross Unrealized Loss - Total	$ (10,168)	$ (10,274)
Number of securities in gross unrealized loss positions | security	2,860	2,840
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	$ 3,458	$ 2,464
Fair Value - 12 Months or Longer	1,145	448
Fair Value - Total	4,603	2,912
Gross Unrealized Loss - Less than 12 Months	(33)	(57)
Gross Unrealized Loss - 12 Months or Longer	(54)	(33)
Gross Unrealized Loss - Total	(87)	(90)
RMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	12,256	23,271
Fair Value - 12 Months or Longer	48,956	36,803
Fair Value - Total	61,212	60,074
Gross Unrealized Loss - Less than 12 Months	(466)	(1,809)
Gross Unrealized Loss - 12 Months or Longer	(8,856)	(7,604)
Gross Unrealized Loss - Total	(9,322)	(9,413)
RMBS, Non-agency
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	9	14
Fair Value - 12 Months or Longer	8	3
Fair Value - Total	17	17
Gross Unrealized Loss - Less than 12 Months	0	(1)
Gross Unrealized Loss - 12 Months or Longer	(1)	0
Gross Unrealized Loss - Total	(1)	(1)
RMBS
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	12,265	23,285
Fair Value - 12 Months or Longer	48,964	36,806
Fair Value - Total	61,229	60,091
Gross Unrealized Loss - Less than 12 Months	(466)	(1,810)
Gross Unrealized Loss - 12 Months or Longer	(8,857)	(7,604)
Gross Unrealized Loss - Total	(9,323)	(9,414)
CMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	1,505	4,325
Fair Value - 12 Months or Longer	5,783	3,214
Fair Value - Total	7,288	7,539
Gross Unrealized Loss - Less than 12 Months	(49)	(267)
Gross Unrealized Loss - 12 Months or Longer	(703)	(493)
Gross Unrealized Loss - Total	(752)	(760)
Other securities
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	765	555
Fair Value - 12 Months or Longer	330	76
Fair Value - Total	1,095	631
Gross Unrealized Loss - Less than 12 Months	(2)	(7)
Gross Unrealized Loss - 12 Months or Longer	(4)	(3)
Gross Unrealized Loss - Total	$ (6)	$ (10)