Investment Securities - Securities in Gross Unrealized Loss Position (Details) $ in Millions	Mar. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	$ 13,407	$ 30,629
Fair Value - 12 Months or Longer	57,627	40,544
Fair Value - Total	71,034	71,173
Gross Unrealized Loss - Less than 12 Months	(329)	(2,141)
Gross Unrealized Loss - 12 Months or Longer	(8,748)	(8,133)
Gross Unrealized Loss - Total	$ (9,077)	$ (10,274)
Number of securities in gross unrealized loss positions | security	2,760	2,840
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	$ 1,059	$ 2,464
Fair Value - 12 Months or Longer	1,155	448
Fair Value - Total	2,214	2,912
Gross Unrealized Loss - Less than 12 Months	(20)	(57)
Gross Unrealized Loss - 12 Months or Longer	(50)	(33)
Gross Unrealized Loss - Total	(70)	(90)
RMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	9,925	23,271
Fair Value - 12 Months or Longer	50,456	36,803
Fair Value - Total	60,381	60,074
Gross Unrealized Loss - Less than 12 Months	(267)	(1,809)
Gross Unrealized Loss - 12 Months or Longer	(8,071)	(7,604)
Gross Unrealized Loss - Total	(8,338)	(9,413)
RMBS, Non-agency
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	8	14
Fair Value - 12 Months or Longer	9	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	9,933	23,285
Fair Value - 12 Months or Longer	50,465	36,806
Fair Value - Total	60,398	60,091
Gross Unrealized Loss - Less than 12 Months	(267)	(1,810)
Gross Unrealized Loss - 12 Months or Longer	(8,072)	(7,604)
Gross Unrealized Loss - Total	(8,339)	(9,414)
CMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	1,884	4,325
Fair Value - 12 Months or Longer	5,633	3,214
Fair Value - Total	7,517	7,539
Gross Unrealized Loss - Less than 12 Months	(42)	(267)
Gross Unrealized Loss - 12 Months or Longer	(619)	(493)
Gross Unrealized Loss - Total	(661)	(760)
Other securities
Debt Securities, Available-for-sale [Line Items]
Fair Value - Less than 12 Months	531	555
Fair Value - 12 Months or Longer	374	76
Fair Value - Total	905	631
Gross Unrealized Loss - Less than 12 Months	0	(7)
Gross Unrealized Loss - 12 Months or Longer	(7)	(3)
Gross Unrealized Loss - Total	$ (7)	$ (10)