Available-for-Sale and Held-to-Maturity Securities (Details - OTTI) - USD ($) $ in Millions | Jun. 30, 2019 | Dec. 31, 2018 |
Debt Securities, Available-for-sale [Line Items] | | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | $ 636 | $ 3,329 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 3,385 | 7,981 |
Debt Securities, Available-for-sale, Unrealized Loss Position | 4,021 | 11,310 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (6) | (35) |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (39) | (279) |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | (45) | (314) |
Schedule of Held-to-maturity Securities [Line Items] | | |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | 305 | 3,675 |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 6,996 | 13,740 |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value | 7,301 | 17,415 |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (2) | (34) |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (68) | (389) |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss | (70) | (423) |
Agency mortgage-backed securities [Member] | | |
Debt Securities, Available-for-sale [Line Items] | | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 448 | 2,945 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 3,327 | 7,826 |
Debt Securities, Available-for-sale, Unrealized Loss Position | 3,775 | 10,771 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (6) | (34) |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (39) | (271) |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | (45) | (305) |
Schedule of Held-to-maturity Securities [Line Items] | | |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | 305 | 2,802 |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 6,154 | 11,587 |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value | 6,459 | 14,389 |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (2) | (31) |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (64) | (332) |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss | (66) | (363) |
Agency debentures [Member] | | |
Debt Securities, Available-for-sale [Line Items] | | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 0 | 383 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 58 | 116 |
Debt Securities, Available-for-sale, Unrealized Loss Position | 58 | 499 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | (1) |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | (6) |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | 0 | (7) |
Schedule of Held-to-maturity Securities [Line Items] | | |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | 0 | 776 |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 443 | 666 |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value | 443 | 1,442 |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | (2) |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (1) | (14) |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss | (1) | (16) |
US Treasuries [Member] | | |
Debt Securities, Available-for-sale [Line Items] | | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 99 | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 0 | |
Debt Securities, Available-for-sale, Unrealized Loss Position | 99 | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | 0 | |
Non-agency asset-backed securities [Member] | | |
Debt Securities, Available-for-sale [Line Items] | | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 89 | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 0 | |
Debt Securities, Available-for-sale, Unrealized Loss Position | 89 | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | 0 | |
Other agency debt securities [Member] | | |
Debt Securities, Available-for-sale [Line Items] | | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | | 30 |
Debt Securities, Available-for-sale, Unrealized Loss Position | | 30 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | | (2) |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | | (2) |
Schedule of Held-to-maturity Securities [Line Items] | | |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value | 0 | 97 |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value | 399 | 1,487 |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value | 399 | 1,584 |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | (1) |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (3) | (43) |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss | $ (3) | (44) |
Municipal bonds [Member] | | |
Debt Securities, Available-for-sale [Line Items] | | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | | 9 |
Debt Securities, Available-for-sale, Unrealized Loss Position | | 9 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | | 0 |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | | 0 |
Other [Member] | | |
Debt Securities, Available-for-sale [Line Items] | | |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | | 1 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | | 0 |
Debt Securities, Available-for-sale, Unrealized Loss Position | | 1 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | | 0 |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | | 0 |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | | $ 0 |