Retirement Plans - Fair Value of Financial Assets of Funded Pension Plans (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	$ 2,374	$ 2,445
Cash and Short-term Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	47	27
U.S. Equities (domestic)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	339	309
International Equities (non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	152	210
Global Equities (domestic and non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	5	61
Treasury and Government Related - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	353	581
Mortgage-backed Securities - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	84	110
Corporate - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	442	550
Private Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	427	414
Real Estate Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	97	183
Bulk Annuity Policy
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	428	0
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	424	388
Level 1 | Cash and Short-term Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	47	27
Level 1 | U.S. Equities (domestic)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	339	309
Level 1 | International Equities (non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	38	52
Level 1 | Global Equities (domestic and non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 1 | Treasury and Government Related - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 1 | Mortgage-backed Securities - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 1 | Corporate - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 1 | Private Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 1 | Real Estate Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 1 | Bulk Annuity Policy
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	872	1,232
Level 2 | Cash and Short-term Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 2 | U.S. Equities (domestic)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 2 | International Equities (non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 2 | Global Equities (domestic and non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	5	6
Level 2 | Treasury and Government Related - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	353	581
Level 2 | Mortgage-backed Securities - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	75	98
Level 2 | Corporate - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	439	547
Level 2 | Private Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 2 | Real Estate Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 2 | Bulk Annuity Policy
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	428	0
Level 3 | Cash and Short-term Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3 | U.S. Equities (domestic)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3 | International Equities (non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3 | Global Equities (domestic and non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3 | Treasury and Government Related - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3 | Mortgage-backed Securities - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3 | Corporate - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3 | Private Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3 | Real Estate Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Level 3 | Bulk Annuity Policy
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	428	0
Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	650	825
Net Asset Value | Cash and Short-term Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Net Asset Value | U.S. Equities (domestic)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Net Asset Value | International Equities (non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	114	158
Net Asset Value | Global Equities (domestic and non-U.S.)
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	55
Net Asset Value | Treasury and Government Related - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	0	0
Net Asset Value | Mortgage-backed Securities - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	9	12
Net Asset Value | Corporate - Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	3	3
Net Asset Value | Private Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	427	414
Net Asset Value | Real Estate Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	97	183
Net Asset Value | Bulk Annuity Policy
Defined Benefit Plan Disclosure [Line Items]
Fair value of financial assets of funded pension plans	$ 0	$ 0