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Pension Plans and Other Postretirement Benefits - Fair Values of Company's Pension Plan Assets by Asset Category (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | $ 3,203 | $ 3,141
Interest and dividend receivable on plan assets | $ 5 | $ 4
Investment Grade Bonds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Investment in mutual funds | 73.00% | 73.00%
High-Yielding Bonds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Investment in mutual funds | 27.00% | 27.00%
Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | $ 2,028 | $ 2,164
Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 690 | 533
Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 485 | 444
Money-market investments |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 76 | 65
Money-market investments | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 50 | 41
Money-market investments | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 26 | 24
Money-market investments | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 1,355 | 1,449
Equity Securities | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 1,355 | 1,449
Equity Securities | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Equity Securities | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
M&T |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 135 | 112
M&T | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 135 | 112
M&T | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
M&T | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Domestic Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 440 | 512
Domestic Equity Securities | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 440 | 512
Domestic Equity Securities | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Domestic Equity Securities | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
International Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 17 | 17
International Equity Securities | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 17 | 17
International Equity Securities | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
International Equity Securities | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Domestic Mutual Fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 282 | 307
Domestic Mutual Fund | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 282 | 307
Domestic Mutual Fund | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Domestic Mutual Fund | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
International Mutual Fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 481 | 501
International Mutual Fund | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 481 | 501
International Mutual Fund | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
International Mutual Fund | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Total Debt Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 944 | 959
Total Debt Securities | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 425 | 450
Total Debt Securities | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 519 | 509
Total Debt Securities | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Corporate Debt Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 222 | 227
Corporate Debt Securities | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Corporate Debt Securities | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 222 | 227
Corporate Debt Securities | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Government |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 281 | 276
Government | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Government | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 281 | 276
Government | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
International |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 16 | 6
International | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
International | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 16 | 6
International | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Domestic Mutual Fund Debt Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 425 | 450
Domestic Mutual Fund Debt Securities | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 425 | 450
Domestic Mutual Fund Debt Securities | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Domestic Mutual Fund Debt Securities | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Other Investments |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 828 | 668
Other Investments | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 198 | 224
Other Investments | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 145 | 0
Other Investments | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 485 | 444
Diversified mutual fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 110 | 110
Diversified mutual fund | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 110 | 110
Diversified mutual fund | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Diversified mutual fund | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Common Collective Trust |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 145 |
Common Collective Trust | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 |
Common Collective Trust | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 145 |
Common Collective Trust | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 |
Real estate partnerships |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 31 | 29
Real estate partnerships | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 5 | 7
Real estate partnerships | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Real estate partnerships | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 26 | 22
Private equity/debt |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 265 | 235
Private equity/debt | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Private equity/debt | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Private equity/debt | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 265 | 235
Hedge funds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 267 | 285
Hedge funds | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 83 | 107
Hedge funds | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Hedge funds | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 184 | 178
Guaranteed deposit fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 10 | 9
Guaranteed deposit fund | Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Guaranteed deposit fund | Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | 0 | 0
Guaranteed deposit fund | Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined benefit plan fair value of plan assets | $ 10 | $ 9

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