Fair Value Measurements - NPC - Debt (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 57,028	$ 52,172
Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	52,594	48,624
NPC | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	3,393	3,392
NPC | Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 3,344	$ 3,417