Fair Value Measurements - NPC (Details) - Recurring - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Assets:
Assets, fair value	$ 6,393	$ 3,566
Investment funds
Assets:
Equity securities	265	283
Money market mutual funds
Assets:
Money market mutual funds	3,613	1,469
Level 1
Assets:
Assets, fair value	5,295	2,648
Level 1 \| Investment funds
Assets:
Equity securities	265	283
Level 1 \| Money market mutual funds
Assets:
Money market mutual funds	3,613	1,469
Level 2
Assets:
Assets, fair value	1,088	916
Level 2 \| Investment funds
Assets:
Equity securities	0	0
Level 2 \| Money market mutual funds
Assets:
Money market mutual funds	0	0
Level 3
Assets:
Assets, fair value	16	10
Level 3 \| Investment funds
Assets:
Equity securities	0	0
Level 3 \| Money market mutual funds
Assets:
Money market mutual funds	0	0
Commodity derivatives \| Level 1
Liabilities:
Commodity derivatives	(13)	(13)
Commodity derivatives \| Level 2
Liabilities:
Commodity derivatives	(134)	(169)
Commodity derivatives \| Level 3
Liabilities:
Commodity derivatives	(68)	(56)
NPC
Assets:
Assets, fair value	195	24
NPC \| Investment funds
Assets:
Equity securities	6	5
NPC \| Money market mutual funds
Assets:
Money market mutual funds	189	19
NPC \| Level 1
Assets:
Assets, fair value	195	24
NPC \| Level 1 \| Investment funds
Assets:
Equity securities	6	5
NPC \| Level 1 \| Money market mutual funds
Assets:
Money market mutual funds	189	19
NPC \| Level 2
Assets:
Assets, fair value	0	0
NPC \| Level 2 \| Investment funds
Assets:
Equity securities	0	0
NPC \| Level 2 \| Money market mutual funds
Assets:
Money market mutual funds	0	0
NPC \| Level 3
Assets:
Assets, fair value	0	0
NPC \| Level 3 \| Investment funds
Assets:
Equity securities	0	0
NPC \| Level 3 \| Money market mutual funds
Assets:
Money market mutual funds	0	0
NPC \| Commodity derivatives
Liabilities:
Commodity derivatives	(49)	(41)
NPC \| Commodity derivatives \| Level 1
Liabilities:
Commodity derivatives	0	0
NPC \| Commodity derivatives \| Level 2
Liabilities:
Commodity derivatives		0
NPC \| Commodity derivatives \| Level 3
Liabilities:
Commodity derivatives	$ (49)	$ (41)