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Investment Securities - Securities in Gross Unrealized Loss Position (Detail) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | $ 15,882 | $ 12,743
Fair Value - 12 Months or Longer | 12,252 | 21,422
Fair Value - Total | 28,134 | 34,165
Gross Unrealized Loss - Less than 12 Months | (120) | (297)
Gross Unrealized Loss - 12 Months or Longer | (212) | (675)
Gross Unrealized Loss - Total | (332) | (972)
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 2,647 | 2,543
Fair Value - 12 Months or Longer | 0 | 1,076
Fair Value - Total | 2,647 | 3,619
Gross Unrealized Loss - Less than 12 Months | (4) | (3)
Gross Unrealized Loss - 12 Months or Longer | 0 | (14)
Gross Unrealized Loss - Total | (4) | (17)
RMBS, Agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 10,494 | 7,863
Fair Value - 12 Months or Longer | 10,567 | 18,118
Fair Value - Total | 21,061 | 25,981
Gross Unrealized Loss - Less than 12 Months | (92) | (260)
Gross Unrealized Loss - 12 Months or Longer | (192) | (609)
Gross Unrealized Loss - Total | (284) | (869)
RMBS, Non-agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 35 | 89
Fair Value - 12 Months or Longer | 16 | 10
Fair Value - Total | 51 | 99
Gross Unrealized Loss - Less than 12 Months | (1) | (2)
Gross Unrealized Loss - 12 Months or Longer | (1) | 0
Gross Unrealized Loss - Total | (2) | (2)
RMBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 10,529 | 7,952
Fair Value - 12 Months or Longer | 10,583 | 18,128
Fair Value - Total | 21,112 | 26,080
Gross Unrealized Loss - Less than 12 Months | (93) | (262)
Gross Unrealized Loss - 12 Months or Longer | (193) | (609)
Gross Unrealized Loss - Total | (286) | (871)
CMBS, Agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 2,580 | 2,004
Fair Value - 12 Months or Longer | 1,563 | 1,540
Fair Value - Total | 4,143 | 3,544
Gross Unrealized Loss - Less than 12 Months | (23) | (31)
Gross Unrealized Loss - 12 Months or Longer | (19) | (47)
Gross Unrealized Loss - Total | (42) | (78)
Other securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 126 | 244
Fair Value - 12 Months or Longer | 106 | 678
Fair Value - Total | 232 | 922
Gross Unrealized Loss - Less than 12 Months | 0 | (1)
Gross Unrealized Loss - 12 Months or Longer | 0 | (5)
Gross Unrealized Loss - Total | $ 0 | $ (6)

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