Consolidated Statements of Changes in Shareholder's Equity (Unaudited) - NPC - USD ($) $ in Millions	Total	NPC	NPC Common Stock	NPC Additional Paid-in Capital	NPC Retained Earnings	NPC Accumulated Other Comprehensive (Loss) Income, Net
Balance (shares) at Dec. 31, 2022			1,000
Balance at Dec. 31, 2022		$ 3,354	$ 0	$ 2,333	$ 1,022	$ (1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 989	4			4
Contributions		400		400
Balance (shares) at Mar. 31, 2023			1,000
Balance at Mar. 31, 2023		$ 3,758	$ 0	2,733	1,026	(1)
Balance (shares) at Dec. 31, 2023	76,000,000	1,000	1,000
Balance at Dec. 31, 2023	$ 48,434	$ 3,964	$ 0	2,733	1,232	(1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 653	15			15
Contributions		$ 100		100
Balance (shares) at Mar. 31, 2024	76,000,000	1,000	1,000
Balance at Mar. 31, 2024	$ 48,959	$ 4,079	$ 0	$ 2,833	$ 1,247	$ (1)