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Investment Securities (Schedule of Unrealized Loss on Investments) (Details) - USD ($) $ in Millions | Jun. 30, 2020 | Dec. 31, 2019
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Debt Securities [Line Items] |  |
Debt Securities, held-to-maturity, less than 12 Months, fair value |  | $ 283
Debt securities, held-to-maturity, unrealized loss, less than 12 Months |  | (6)
Debt Securities, held-to-maturity, 12 Months or Longer, fair value |  | 3
Debt securities, held-to-maturity, unrealized loss, 12 months or longer |  | 0
Debt securities, available-for-sale, fair value, less than 12 months | $ 972 | 7,012
Debt securities, available-for-sale, unrealized loss, less than 12 months | (14) | (46)
Debt securities, available-for-sale, fair value, 12 months or longer | 25 | 1,450
Debt securities, available-for-sale, unrealized loss, 12 months or longer | (2) | (27)
US Treasury |  |
Debt Securities [Line Items] |  |
Debt securities, available-for-sale, fair value, less than 12 months | 9 | 1,267
Debt securities, available-for-sale, unrealized loss, less than 12 months | 0 | (11)
Debt securities, available-for-sale, fair value, 12 months or longer | 0 | 279
Debt securities, available-for-sale, unrealized loss, 12 months or longer | 0 | (6)
US States and political subdivisions |  |
Debt Securities [Line Items] |  |
Debt securities, available-for-sale, fair value, less than 12 months | 55 | 72
Debt securities, available-for-sale, unrealized loss, less than 12 months | 0 | (1)
Debt securities, available-for-sale, fair value, 12 months or longer | 5 | 5
Debt securities, available-for-sale, unrealized loss, 12 months or longer | (1) | 0
Foreign government |  |
Debt Securities [Line Items] |  |
Debt securities, available-for-sale, fair value, less than 12 months | 2 | 40
Debt securities, available-for-sale, unrealized loss, less than 12 months | 0 | (1)
Debt securities, available-for-sale, fair value, 12 months or longer | 0 | 3
Debt securities, available-for-sale, unrealized loss, 12 months or longer | 0 | 0
Agency mortgage-backed residential |  |
Debt Securities [Line Items] |  |
Debt Securities, held-to-maturity, less than 12 Months, fair value |  | 283
Debt securities, held-to-maturity, unrealized loss, less than 12 Months |  | (6)
Debt Securities, held-to-maturity, 12 Months or Longer, fair value |  | 0
Debt securities, held-to-maturity, unrealized loss, 12 months or longer |  | 0
Debt securities, available-for-sale, fair value, less than 12 months | 404 | 4,606
Debt securities, available-for-sale, unrealized loss, less than 12 months | (4) | (23)
Debt securities, available-for-sale, fair value, 12 months or longer | 5 | 908
Debt securities, available-for-sale, unrealized loss, 12 months or longer | 0 | (13)
Mortgage-backed residential |  |
Debt Securities [Line Items] |  |
Debt securities, available-for-sale, fair value, less than 12 months | 350 | 613
Debt securities, available-for-sale, unrealized loss, less than 12 months | (4) | (4)
Debt securities, available-for-sale, fair value, 12 months or longer | 0 | 203
Debt securities, available-for-sale, unrealized loss, 12 months or longer | 0 | (7)
Agency mortgage-backed commercial |  |
Debt Securities [Line Items] |  |
Debt securities, available-for-sale, fair value, less than 12 months | 0 | 335
Debt securities, available-for-sale, unrealized loss, less than 12 months | 0 | (6)
Debt securities, available-for-sale, fair value, 12 months or longer | 0 | 0
Debt securities, available-for-sale, unrealized loss, 12 months or longer | 0 | 0
Mortgage-backed commercial |  |
Debt Securities [Line Items] |  |
Debt securities, available-for-sale, fair value, less than 12 months | 34 | 0
Debt securities, available-for-sale, unrealized loss, less than 12 months | (3) | 0
Debt securities, available-for-sale, fair value, 12 months or longer | 0 | 0
Debt securities, available-for-sale, unrealized loss, 12 months or longer | 0 | 0
Asset-backed |  |
Debt Securities [Line Items] |  |
Debt Securities, held-to-maturity, less than 12 Months, fair value |  | 0
Debt securities, held-to-maturity, unrealized loss, less than 12 Months |  | 0
Debt Securities, held-to-maturity, 12 Months or Longer, fair value |  | 3
Debt securities, held-to-maturity, unrealized loss, 12 months or longer |  | 0
Debt securities, available-for-sale, fair value, less than 12 months | 38 | 8
Debt securities, available-for-sale, unrealized loss, less than 12 months | 0 | 0
Debt securities, available-for-sale, fair value, 12 months or longer | 1 | 11
Debt securities, available-for-sale, unrealized loss, 12 months or longer | 0 | 0
Corporate debt |  |
Debt Securities [Line Items] |  |
Debt securities, available-for-sale, fair value, less than 12 months | 80 | 71
Debt securities, available-for-sale, unrealized loss, less than 12 months | (3) | 0
Debt securities, available-for-sale, fair value, 12 months or longer | 14 | 41
Debt securities, available-for-sale, unrealized loss, 12 months or longer | $ (1) | $ (1)

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