Income Taxes - Additional Information (Detail) - USD ($)		12 Months Ended
	Sep. 14, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Federal statutory tax rate		21.00%	21.00%	21.00%
Regulatory liability due to obligation to transfer tax rate reduction expense benefit		$ 7,000,000
Provision for income taxes		121,000,000	$ 80,000,000	$ 82,000,000
General business credit		$ 304,000,000
Deferred tax general business credits expiration date		2027-2042
Investment tax credits		$ 264,000,000
Investment tax credit expiration date		2034 and 2041
Uncertain tax positions		$ 9,000,000	6,000,000	9,000,000	$ 9,000,000
Unrecognized tax benefits decreased			0	2,000,000
Pre-tax charges (benefits)		0	0	0
Interest accrued		0	0	0
Penalties		$ 0	0	0
Statutes of limitations		3 years
Income tax examination period		1 year
Decrease in current income tax expense		$ (59,000,000)
Federal [Member] | R&D Tax Credits [Member]
Income Taxes [Line Items]
Uncertain tax positions		$ 9,000,000	6,000,000
Unrecognized tax benefits decreased			$ 5,000,000	$ 2,000,000
Florida [Member]
Income Taxes [Line Items]
Florida corporate income tax rate	4.46%	5.50%	3.53%
Regulatory liability due to obligation to transfer tax rate reduction expense benefit			$ 4,000,000