Statements of Consolidated Comprehensive Income (Loss) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Income		$ 674.4	$ 791.8	$ 588.8
Other comprehensive income:
Net unrealized gain (loss) on available-for-sale securities	[1]	3.9	(13.3)	(3.9)
Net unrealized gain (loss) on cash flow hedges	[2]	(0.2)	109.9	25.4
Unrecognized pension and OPEB benefit (costs)	[3]	(0.2)	(6.9)	8.4
Total other comprehensive income		3.5	89.7	29.9
Total Comprehensive Income		$ 677.9	$ 881.5	$ 618.7

[1] Net unrealized gain (loss) on available-for-sale securities, net of $1.0 million tax expense, $3.5 million tax benefit and $1.0 million tax benefit in 2023, 2022 and 2021, respectively.

[2] Net unrealized (loss) gain on derivatives qualifying as cash flow hedges, net of $0.1 million tax benefit, $36.4 million tax expense and $8.4 million tax expense in 2023, 2022 and 2021, respectively.

[3] Unrecognized pension and OPEB benefit (costs), net of $0.1 million tax benefit, $2.3 million tax benefit and $3.8 million tax expense in 2023, 2022 and 2021, respectively.