Long term debt (Details) - USD ($) $ in Millions				12 Months Ended
	Nov. 30, 2023	Aug. 29, 2023	Jan. 13, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt	$ 200	$ 500	$ 100	$ 600	$ 360	$ 400
Long-term Debt, Current Maturities				80	260
Repayments of Long-term Debt				260	0	$ 160
Pollution Control Revenue Bonds at 2,125%				98
Pollution Control Revenue Bonds at 2.375%				21
Pollution Control Revenue Bonds, rates at 2.13% and 2.38%, due 2033				$ 119	$ 119
2030 Member [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt		50
2033 Member
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt		150
2038 Member
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt		100
2059 Member
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt		100
2053 Member
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt		$ 100