XML 39 R28.htm IDEA: XBRL DOCUMENT
v3.24.3

Investment securities (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract] |
Amortized Cost and Estimated Fair Value of Investment Securities | The amortized cost and estimated fair value of investment securities were as follows:
(Dollars in millions) | Amortized Cost |  | Gross Unrealized Gains |  | Gross Unrealized Losses |  | Estimated Fair Value
September 30, 2024 |  |  |  |  |  |  |
Investment securities available for sale: |  |  |  |  |  |  |
U.S. Treasury and federal agencies | $ | 7,824 |  |  | $ | 62 |  |  | $ | 26 |  |  | $ | 7,860 |
Mortgage-backed securities: |  |  |  |  |  |  |
Government issued or guaranteed: |  |  |  |  |  |  |
Commercial | 3,125 |  |  | 55 |  |  | 3 |  |  | 3,177 |
Residential | 5,606 |  |  | 60 |  |  | 77 |  |  | 5,589 |
Other debt securities | 103 |  |  | — |  |  | 2 |  |  | 101 |
| 16,658 |  |  | 177 |  |  | 108 |  |  | 16,727 |
Investment securities held to maturity: |  |  |  |  |  |  |
U.S. Treasury and federal agencies | 1,013 |  |  | — |  |  | 14 |  |  | 999 |
Obligations of states and political subdivisions | 2,397 |  |  | — |  |  | 71 |  |  | 2,326 |
Mortgage-backed securities: |  |  |  |  |  |  |
Government issued or guaranteed: |  |  |  |  |  |  |
Commercial | 2,038 |  |  | — |  |  | 81 |  |  | 1,957 |
Residential | 9,016 |  |  | 13 |  |  | 646 |  |  | 8,383 |
Privately issued | 38 |  |  | 8 |  |  | 3 |  |  | 43 |
Other debt securities | 1 |  |  | — |  |  | — |  |  | 1 |
| 14,503 |  |  | 21 |  |  | 815 |  |  | 13,709 |
Total debt securities | $ | 31,161 |  |  | $ | 198 |  |  | $ | 923 |  |  | $ | 30,436 |
Equity and other securities: |  |  |  |  |  |  |
Readily marketable equity — at fair value | $ | 250 |  |  | $ | 9 |  |  | $ | 2 |  |  | $ | 257 |
Other — at cost | 840 |  |  | — |  |  | — |  |  | 840 |
Total equity and other securities | $ | 1,090 |  |  | $ | 9 |  |  | $ | 2 |  |  | $ | 1,097 |
December 31, 2023 |  |  |  |  |  |  |
Investment securities available for sale: |  |  |  |  |  |  |
U.S. Treasury and federal agencies | $ | 7,818 |  |  | $ | — |  |  | $ | 113 |  |  | $ | 7,705 |
Mortgage-backed securities: |  |  |  |  |  |  |
Government issued or guaranteed: |  |  |  |  |  |  |
Commercial | 425 |  |  | — |  |  | 9 |  |  | 416 |
Residential | 2,272 |  |  | — |  |  | 118 |  |  | 2,154 |
Other debt securities | 176 |  |  | — |  |  | 11 |  |  | 165 |
| 10,691 |  |  | — |  |  | 251 |  |  | 10,440 |
Investment securities held to maturity: |  |  |  |  |  |  |
U.S. Treasury and federal agencies | 1,005 |  |  | — |  |  | 31 |  |  | 974 |
Obligations of states and political subdivisions | 2,501 |  |  | — |  |  | 67 |  |  | 2,434 |
Mortgage-backed securities: |  |  |  |  |  |  |
Government issued or guaranteed: |  |  |  |  |  |  |
Commercial | 2,033 |  |  | — |  |  | 130 |  |  | 1,903 |
Residential | 9,747 |  |  | 4 |  |  | 802 |  |  | 8,949 |
Privately issued | 42 |  |  | 9 |  |  | 5 |  |  | 46 |
Other debt securities | 2 |  |  | — |  |  | — |  |  | 2 |
| 15,330 |  |  | 13 |  |  | 1,035 |  |  | 14,308 |
Total debt securities | $ | 26,021 |  |  | $ | 13 |  |  | $ | 1,286 |  |  | $ | 24,748 |
Equity and other securities: |  |  |  |  |  |  |
Readily marketable equity — at fair value | $ | 266 |  |  | $ | 5 |  |  | $ | 3 |  |  | $ | 268 |
Other — at cost | 859 |  |  | — |  |  | — |  |  | 859 |
Total equity and other securities | $ | 1,125 |  |  | $ | 5 |  |  | $ | 3 |  |  | $ | 1,127 |
Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity | At September 30, 2024, the amortized cost and estimated fair value of debt securities by contractual maturity were as follows:
(Dollars in millions) | Amortized Cost |  | Estimated Fair Value
Debt securities available for sale: |  |  |
Due in one year or less | $ | 3,206 |  |  | $ | 3,187 |
Due after one year through five years | 4,721 |  |  | 4,774 |
Due after five years through ten years | — |  |  | — |
Due after ten years | — |  |  | — |
| 7,927 |  |  | 7,961 |
Mortgage-backed securities | 8,731 |  |  | 8,766 |
| $ | 16,658 |  |  | $ | 16,727 |
Debt securities held to maturity: |  |  |
Due in one year or less | $ | 589 |  |  | $ | 585 |
Due after one year through five years | 654 |  |  | 643 |
Due after five years through ten years | 1,463 |  |  | 1,429 |
Due after ten years | 705 |  |  | 669 |
| 3,411 |  |  | 3,326 |
Mortgage-backed securities | 11,092 |  |  | 10,383 |
| $ | 14,503 |  |  | $ | 13,709 |
Investment Securities in Continuous Unrealized Loss Position | A summary of investment securities that as of September 30, 2024 and December 31, 2023 had been in a continuous unrealized loss position for less than twelve months and those that had been in a continuous unrealized loss position for twelve months or longer follows:
| Less Than 12 Months |  | 12 Months or More
(Dollars in millions) | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses
September 30, 2024 |  |  |  |  |  |  |
Investment securities available for sale: |  |  |  |  |  |  |
U.S. Treasury and federal agencies | $ | 125 |  |  | $ | — |  |  | $ | 3,069 |  |  | $ | 26 |
Mortgage-backed securities: |  |  |  |  |  |  |
Government issued or guaranteed: |  |  |  |  |  |  |
Commercial | 395 |  |  | 2 |  |  | 128 |  |  | 1 |
Residential | 227 |  |  | — |  |  | 1,760 |  |  | 77 |
Other debt securities | — |  |  | — |  |  | 64 |  |  | 2 |
| 747 |  |  | 2 |  |  | 5,021 |  |  | 106 |
Investment securities held to maturity: |  |  |  |  |  |  |
U.S. Treasury and federal agencies | — |  |  | — |  |  | 949 |  |  | 14 |
Obligations of states and political subdivisions | 26 |  |  | — |  |  | 2,192 |  |  | 71 |
Mortgage-backed securities: |  |  |  |  |  |  |
Government issued or guaranteed: |  |  |  |  |  |  |
Commercial | — |  |  | — |  |  | 1,957 |  |  | 81 |
Residential | — |  |  | — |  |  | 7,318 |  |  | 646 |
Privately issued | — |  |  | — |  |  | 31 |  |  | 3 |
| 26 |  |  | — |  |  | 12,447 |  |  | 815 |
Total | $ | 773 |  |  | $ | 2 |  |  | $ | 17,468 |  |  | $ | 921 |
December 31, 2023 |  |  |  |  |  |  |
Investment securities available for sale: |  |  |  |  |  |  |
U.S. Treasury and federal agencies | $ | 229 |  |  | $ | 1 |  |  | $ | 7,474 |  |  | $ | 112 |
Mortgage-backed securities: |  |  |  |  |  |  |
Government issued or guaranteed: |  |  |  |  |  |  |
Commercial | 74 |  |  | 1 |  |  | 330 |  |  | 8 |
Residential | 151 |  |  | 2 |  |  | 1,959 |  |  | 116 |
Other debt securities | 6 |  |  | — |  |  | 154 |  |  | 11 |
| 460 |  |  | 4 |  |  | 9,917 |  |  | 247 |
Investment securities held to maturity: |  |  |  |  |  |  |
U.S. Treasury and federal agencies | 50 |  |  | — |  |  | 924 |  |  | 31 |
Obligations of states and political subdivisions | 218 |  |  | 3 |  |  | 2,172 |  |  | 64 |
Mortgage-backed securities: |  |  |  |  |  |  |
Government issued or guaranteed: |  |  |  |  |  |  |
Commercial | 328 |  |  | 9 |  |  | 1,575 |  |  | 121 |
Residential | 955 |  |  | 11 |  |  | 7,139 |  |  | 791 |
Privately issued | — |  |  | — |  |  | 34 |  |  | 5 |
| 1,551 |  |  | 23 |  |  | 11,844 |  |  | 1,012 |
Total | $ | 2,011 |  |  | $ | 27 |  |  | $ | 21,761 |  |  | $ | 1,259 |

X
- Definition Amortized cost and estimated fair value of debt securities by contractual maturity. + References No definition available. + Details
Name: | mtb_AmortizedCostAndEstimatedFairValueOfDebtSecuritiesByContractualMaturityTableTextBlock
Namespace Prefix: | mtb_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortized cost and estimated fair value of investment securities. + References No definition available. + Details
Name: | mtb_AmortizedCostAndEstimatedFairValueOfInvestmentSecuritiesTableTextBlock
Namespace Prefix: | mtb_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Investment securities in continuous unrealized loss position. + References No definition available. + Details
Name: | mtb_InvestmentSecuritiesInContinuousUnrealizedLossPositionTableTextBlock
Namespace Prefix: | mtb_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration