Consolidated Statements of Changes in Equity (Unaudited) - NPC - USD ($) $ in Millions	Total	Additional Paid-in Capital	Retained Earnings	NPC	NPC Common Stock	NPC Additional Paid-in Capital	NPC Retained Earnings	NPC Accumulated Other Comprehensive (Loss) Income, Net
Balance (shares) at Dec. 31, 2019					1,000
Balance at Dec. 31, 2019				$ 2,797	$ 0	$ 2,308	$ 493	$ (4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 1,786			79			79
Dividends declared				(85)			(85)
Other equity transactions	(1)	$ (1)		1			1
Balance (shares) at Jun. 30, 2020					1,000
Balance at Jun. 30, 2020				2,792	$ 0	2,308	488	(4)
Balance (shares) at Mar. 31, 2020					1,000
Balance at Mar. 31, 2020				2,794	$ 0	2,308	490	(4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 1,116			83			83
Dividends declared				(85)			(85)
Balance (shares) at Jun. 30, 2020					1,000
Balance at Jun. 30, 2020				$ 2,792	$ 0	2,308	488	(4)
Balance (shares) at Dec. 31, 2020	76,000,000			1,000	1,000
Balance at Dec. 31, 2020	$ 43,010			$ 2,939	$ 0	2,308	634	(3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,285			84			84
Dividends declared				$ (13)			(13)
Other equity transactions	$ (1)
Balance (shares) at Jun. 30, 2021	76,000,000			1,000	1,000
Balance at Jun. 30, 2021	$ 45,412			$ 3,010	$ 0	2,308	705	(3)
Balance (shares) at Mar. 31, 2021					1,000
Balance at Mar. 31, 2021				2,941	$ 0	2,308	636	(3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,281			82			82
Dividends declared				$ (13)			(13)
Other equity transactions	$ (4)		$ (1)
Balance (shares) at Jun. 30, 2021	76,000,000			1,000	1,000
Balance at Jun. 30, 2021	$ 45,412			$ 3,010	$ 0	$ 2,308	$ 705	$ (3)