| Securities |
mortized cost, gross unrealized gains and losses, and estimated fair value of debt securities held to maturity and debt securities available for sale are as follows: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | December 31, 2019 | | | | Recognized in OCI (1) | | | | Not recognized in OCI | | | | Amortized Cost | | Gross Unrealized Gains | | Gross Unrealized Losses | | Carrying Value | | Gross Unrealized Gains | | Gross Unrealized Losses | | Estimated Fair Value | | (In millions) | Debt securities held to maturity: | | | | | | | | | | | | | | Mortgage-backed securities: | | | | | | | | | | | | | | Residential agency | $ | 736 |
| | $ | — |
| | $ | (26 | ) | | $ | 710 |
| | $ | 22 |
| | $ | — |
| | $ | 732 |
| Commercial agency | 625 |
| | — |
| | (3 | ) | | 622 |
| | 20 |
| | (2 | ) | | 640 |
| | $ | 1,361 |
| | $ | — |
| | $ | (29 | ) | | $ | 1,332 |
| | $ | 42 |
| | $ | (2 | ) | | $ | 1,372 |
| | | | | | | | | | | | | | | Debt securities available for sale: | | | | | | | | | | | | | | U.S. Treasury securities | $ | 180 |
| | $ | 2 |
| | $ | — |
| | $ | 182 |
| | | | | | $ | 182 |
| Federal agency securities | 42 |
| | 1 |
| | — |
| | 43 |
| | | | | | 43 |
| Mortgage-backed securities: | | | | | | | | | | | | | | Residential agency | 15,336 |
| | 218 |
| | (38 | ) | | 15,516 |
| | | | | | 15,516 |
| Residential non-agency | 1 |
| | — |
| | — |
| | 1 |
| | | | | | 1 |
| Commercial agency | 4,720 |
| | 77 |
| | (31 | ) | | 4,766 |
| | | | | | 4,766 |
| Commercial non-agency | 639 |
| | 8 |
| | — |
| | 647 |
| | | | | | 647 |
| Corporate and other debt securities | 1,414 |
| | 38 |
| | (1 | ) | | 1,451 |
| | | | | | 1,451 |
| | $ | 22,332 |
| | $ | 344 |
| | $ | (70 | ) | | $ | 22,606 |
| | | | | | $ | 22,606 |
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | December 31, 2018 | | | | Recognized in OCI (1) | | | | Not recognized in OCI | | | | Amortized
Cost | | Gross Unrealized Gains | | Gross Unrealized Losses | | Carrying Value | | Gross
Unrealized
Gains | | Gross
Unrealized
Losses | | Estimated
Fair
Value | | (In millions) | Debt securities held to maturity: | | | | | | | | | | | | | | Mortgage-backed securities: | | | | | | | | | | | | | | Residential agency | $ | 883 |
| | $ | — |
| | $ | (32 | ) | | $ | 851 |
| | $ | 1 |
| | $ | (10 | ) | | $ | 842 |
| Commercial agency | 634 |
| | — |
| | (3 | ) | | 631 |
| | — |
| | (13 | ) | | 618 |
| | $ | 1,517 |
| | $ | — |
| | $ | (35 | ) | | $ | 1,482 |
| | $ | 1 |
| | $ | (23 | ) | | $ | 1,460 |
| | | | | | | | | | | | | | | Debt securities available for sale: | | | | | | | | | | | | | | U.S. Treasury securities | $ | 284 |
| | $ | — |
| | $ | (4 | ) | | $ | 280 |
| | | | | | $ | 280 |
| Federal agency securities | 43 |
| | — |
| | — |
| | 43 |
| | | | | | 43 |
| Mortgage-backed securities: | | | | | | | | | | | | | | Residential agency | 17,064 |
| | 26 |
| | (466 | ) | | 16,624 |
| | | | | | 16,624 |
| Residential non-agency | 2 |
| | — |
| | — |
| | 2 |
| | | | | | 2 |
| Commercial agency | 3,891 |
| | 8 |
| | (64 | ) | | 3,835 |
| | | | | | 3,835 |
| Commercial non-agency | 768 |
| | 2 |
| | (10 | ) | | 760 |
| | | | | | 760 |
| Corporate and other debt securities | 1,206 |
| | 2 |
| | (23 | ) | | 1,185 |
| | | | | | 1,185 |
| | $ | 23,258 |
| | $ | 38 |
| | $ | (567 | ) | | $ | 22,729 |
| | | | | | $ | 22,729 |
|
_________ | | (1) | The gross unrealized losses recognized in OCI on securities held to maturity resulted from a transfer of securities available for sale to held to maturity in the second quarter of 2013. |
Debt securities with carrying values of $8.3 billion and $7.9 billion at December 31, 2019 and 2018, respectively, were pledged to secure public funds, trust deposits and certain borrowing arrangements. Included within total pledged securities is approximately $24 million of encumbered U.S. Treasury securities at both December 31, 2019 and 2018. The amortized cost and estimated fair value of debt securities held to maturity and debt securities available for sale at December 31, 2019, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. | | | | | | | | | | Amortized Cost | | Estimated Fair Value | | (In millions) | Debt securities held to maturity: | | | | Mortgage-backed securities: | | | | Residential agency | $ | 736 |
| | $ | 732 |
| Commercial agency | 625 |
| | 640 |
| | $ | 1,361 |
| | $ | 1,372 |
| Debt securities available for sale: | | | | Due in one year or less | $ | 79 |
| | $ | 79 |
| Due after one year through five years | 1,089 |
| | 1,110 |
| Due after five years through ten years | 415 |
| | 432 |
| Due after ten years | 53 |
| | 55 |
| Mortgage-backed securities: | | | | Residential agency | 15,336 |
| | 15,516 |
| Residential non-agency | 1 |
| | 1 |
| Commercial agency | 4,720 |
| | 4,766 |
| Commercial non-agency | 639 |
| | 647 |
| | $ | 22,332 |
| | $ | 22,606 |
|
The following tables present gross unrealized losses and the related estimated fair value of debt securities held to maturity and debt securities available for sale at December 31, 2019 and 2018. For debt securities transferred to held to maturity from available for sale, the analysis in the tables below is comparing the securities' original amortized cost to its current estimated fair value. These securities are segregated between investments that have been in a continuous unrealized loss position for less than twelve months and for twelve months or more. | | | | | | | | | | | | | | | | | | | | | | | | | | December 31, 2019 | | Less Than Twelve Months | | Twelve Months or More | | Total | | Estimated Fair Value | | Gross Unrealized Losses | | Estimated Fair Value | | Gross Unrealized Losses | | Estimated Fair Value | | Gross Unrealized Losses | | (In millions) | Debt securities held to maturity: | | | | | | | | | | | | Mortgage-backed securities: | | | | | | | | | | | | Residential agency | $ | 82 |
| | $ | — |
| | $ | 501 |
| | $ | (5 | ) | | $ | 583 |
| | $ | (5 | ) | Commercial agency | — |
| | — |
| | 127 |
| | (5 | ) | | 127 |
| | (5 | ) | | $ | 82 |
| | $ | — |
| | $ | 628 |
| | $ | (10 | ) | | $ | 710 |
| | $ | (10 | ) | | | | | | | | | | | | | Debt securities available for sale: | | | | | | | | | | | | Mortgage-backed securities: | | | | | | | | | | | | Residential agency | 2,402 |
| | (11 | ) | | 2,505 |
| | (27 | ) | | 4,907 |
| | (38 | ) | Commercial agency | 1,449 |
| | (31 | ) | | 73 |
| | — |
| | 1,522 |
| | (31 | ) | Corporate and other debt securities | 19 |
| | — |
| | 32 |
| | (1 | ) | | 51 |
| | (1 | ) | | $ | 3,870 |
| | $ | (42 | ) | | $ | 2,610 |
| | $ | (28 | ) | | $ | 6,480 |
| | $ | (70 | ) |
| | | | | | | | | | | | | | | | | | | | | | | | | | December 31, 2018 | | Less Than Twelve Months | | Twelve Months or More | | Total | | Estimated Fair Value | | Gross Unrealized Losses | | Estimated Fair Value | | Gross Unrealized Losses | | Estimated Fair Value | | Gross Unrealized Losses | | (In millions) | Debt securities held to maturity: | | | | | | | | | | | | Mortgage-backed securities: | | | | | | | | | | | | Residential agency | $ | — |
| | $ | — |
| | $ | 842 |
| | $ | (42 | ) | | $ | 842 |
| | $ | (42 | ) | Commercial agency | 486 |
| | (7 | ) | | 132 |
| | (9 | ) | | 618 |
| | (16 | ) | | $ | 486 |
| | $ | (7 | ) | | $ | 974 |
| | $ | (51 | ) | | $ | 1,460 |
| | $ | (58 | ) | | | | | | | | | | | | | Debt securities available for sale: | | | | | | | | | | | | U.S. Treasury securities | $ | — |
| | $ | — |
| | $ | 261 |
| | $ | (4 | ) | | $ | 261 |
| | $ | (4 | ) | Mortgage-backed securities: | | | | | | | | | | | | Residential agency | 2,830 |
| | (37 | ) | | 11,010 |
| | (429 | ) | | 13,840 |
| | (466 | ) | Commercial agency | 1,073 |
| | (13 | ) | | 2,254 |
| | (51 | ) | | 3,327 |
| | (64 | ) | Commercial non-agency | 229 |
| | (1 | ) | | 404 |
| | (9 | ) | | 633 |
| | (10 | ) | Corporate and other debt securities | 659 |
| | (11 | ) | | 310 |
| | (12 | ) | | 969 |
| | (23 | ) | | $ | 4,791 |
| | $ | (62 | ) | | $ | 14,239 |
| | $ | (505 | ) | | $ | 19,030 |
| | $ | (567 | ) |
The number of individual debt positions in an unrealized loss position in the tables above decreased from 1,379 at December 31, 2018 to 500 at December 31, 2019. The decrease in the number of securities and the total amount of gross unrealized losses was primarily due to changes in market interest rates. In instances where an unrealized loss existed, there was no indication of an adverse change in credit on the underlying positions in the tables above. As it relates to these positions, management believes no individual unrealized loss, other than those discussed below, represented an OTTI as of those dates. The Company does not intend to sell, and it is not more likely than not that the Company will be required to sell, the positions before the recovery of their amortized cost basis, which may be at maturity. As part of the Company's normal process for evaluating OTTI, management did identify a limited number of positions where an OTTI was believed to exist during 2019. Gross realized gains and gross realized losses on sales of debt securities available for sale from continuing operations are shown in the table below. The cost of securities sold is based on the specific identification method. | | | | | | | | | | | | | | 2019 | | 2018 | | 2017 | | (In millions) | Gross realized gains | $ | 16 |
| | $ | 4 |
| | $ | 22 |
| Gross realized losses | (43 | ) | | (1 | ) | | (5 | ) | OTTI | (1 | ) | | (2 | ) | | (1 | ) | Debt securities available for sale gains (losses), net (1) | $ | (28 | ) | | $ | 1 |
| | $ | 16 |
|
_________ (1) The securities gains (losses), net balances above exclude net trading securities gains of $3 million recognized during 2017.
|