Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Schedule of Investments [Line Items]
Cash	$ 445	$ 629
Balance Sheet Location [Axis]: us-gaap:CashAndCashEquivalentsAtCarryingValue
Cash equivalents:
Cost Basis	2,042	1,982
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	2,042	1,982
U.S. and Canadian government obligations | Balance Sheet Location [Axis]: us-gaap:CashAndCashEquivalentsAtCarryingValue
Cash equivalents:
Cost Basis	277	284
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	277	284
Other debt securities | Balance Sheet Location [Axis]: us-gaap:CashAndCashEquivalentsAtCarryingValue
Cash equivalents:
Cost Basis	1,320	1,069
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	1,320	1,069
Nonqualified employee benefit trusts
Cash equivalents:
Cost Basis	15	15
Unrealized Gains	3	3
Unrealized Losses	0	0
Fair Value	$ 18	$ 18