Consolidated Balance Sheets (Unaudited) - NPC (Parenthetical) - $ / shares	Sep. 30, 2023	Dec. 31, 2022
Common stock, shares authorized (in shares)	115,000,000	115,000,000
Common stock, shares issued (in shares)	76,000,000	76,000,000
Common stock, shares outstanding (in shares)	76,000,000	76,000,000
NPC
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares authorized (in shares)	1,000	1,000
Common stock, shares issued (in shares)	1,000	1,000
Common stock, shares outstanding (in shares)	1,000	1,000