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Investment Securities - Securities in Gross Unrealized Loss Position (Detail) $ in Millions | Mar. 31, 2020 USD ($) Security | Dec. 31, 2019 USD ($)
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | $ 4,087 | $ 15,882
Fair Value - 12 Months or Longer | 6,199 | 12,252
Fair Value - Total | 10,286 | 28,134
Gross Unrealized Loss - Less than 12 Months | (59) | (120)
Gross Unrealized Loss - 12 Months or Longer | (86) | (212)
Gross Unrealized Loss - Total | $ (145) | (332)
Number of securities in gross unrealized loss positions | Security | 590 |
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months |  | 2,647
Fair Value - 12 Months or Longer |  | 0
Fair Value - Total |  | 2,647
Gross Unrealized Loss - Less than 12 Months |  | (4)
Gross Unrealized Loss - 12 Months or Longer |  | 0
Gross Unrealized Loss - Total |  | (4)
RMBS, Agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | $ 1,970 | 10,494
Fair Value - 12 Months or Longer | 5,214 | 10,567
Fair Value - Total | 7,184 | 21,061
Gross Unrealized Loss - Less than 12 Months | (29) | (92)
Gross Unrealized Loss - 12 Months or Longer | (74) | (192)
Gross Unrealized Loss - Total | (103) | (284)
RMBS, Non-agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 211 | 35
Fair Value - 12 Months or Longer | 0 | 16
Fair Value - Total | 211 | 51
Gross Unrealized Loss - Less than 12 Months | (12) | (1)
Gross Unrealized Loss - 12 Months or Longer | 0 | (1)
Gross Unrealized Loss - Total | (12) | (2)
RMBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 2,181 | 10,529
Fair Value - 12 Months or Longer | 5,214 | 10,583
Fair Value - Total | 7,395 | 21,112
Gross Unrealized Loss - Less than 12 Months | (41) | (93)
Gross Unrealized Loss - 12 Months or Longer | (74) | (193)
Gross Unrealized Loss - Total | (115) | (286)
CMBS, Agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 1,351 | 2,580
Fair Value - 12 Months or Longer | 985 | 1,563
Fair Value - Total | 2,336 | 4,143
Gross Unrealized Loss - Less than 12 Months | (14) | (23)
Gross Unrealized Loss - 12 Months or Longer | (12) | (19)
Gross Unrealized Loss - Total | (26) | (42)
Other securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 555 | 126
Fair Value - 12 Months or Longer | 0 | 106
Fair Value - Total | 555 | 232
Gross Unrealized Loss - Less than 12 Months | (4) | 0
Gross Unrealized Loss - 12 Months or Longer | 0 | 0
Gross Unrealized Loss - Total | $ (4) | $ 0

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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 + Details
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