SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF PARENT COMPANY - CONDENSED STATEMENTS OF CASH FLOWS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Adjustments to Reconcile Net Income to Net Cash Flows from Operating Activities:
Depreciation and Amortization	$ 3,289.9	$ 3,090.4	$ 3,202.8
Deferred Income Taxes	58.3	185.1	(137.2)
Loss on the Expected Sale of the Kentucky Operations	0.0	0.0	363.3
Change in Other Noncurrent Assets	(347.6)	(465.1)	(187.7)
Change in Other Noncurrent Liabilities	306.3	29.0	337.8
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(156.0)	236.5	(681.7)
Accounts Payable	85.1	(253.2)	489.2
Other Current Assets	(13.2)	(43.9)	109.0
Other Current Liabilities	182.6	(161.4)	54.3
Net Cash Flows from Operating Activities	6,804.3	5,012.2	5,288.0
INVESTING ACTIVITIES
Construction Expenditures	(7,630.7)	(7,378.3)	(6,671.7)
Other Investing Activities	141.9	122.1	50.3
Net Cash Flows Used for Investing Activities	(7,596.5)	(6,266.7)	(7,751.8)
FINANCING ACTIVITIES
Issuance of Common Stock, Net	552.1	999.6	826.5
Issuance of Long-term Debt	5,117.0	5,462.8	4,649.7
Issuance of Short-term Debt with Original Maturities greater than 90 Days	723.8	1,069.9	833.9
Change in Short-term Debt with Original Maturities less than 90 Day, Net	(159.1)	(1,223.1)	1,650.4
Retirement of Long-term Debt	(2,685.0)	(2,196.1)	(2,345.4)
Redemption of Short-term Debt with Original Maturities greater than 90 Days	(871.1)	(1,128.8)	(986.1)
Dividends Paid on Common Stock	(1,903.9)	(1,760.4)	(1,645.2)
Other Financing Activities	(49.8)	(78.6)	(105.4)
Net Cash Flows from Financing Activities	659.2	1,077.0	2,568.9
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(133.0)	(177.5)	105.1
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	379.0	556.5	451.4
Cash, Cash Equivalents and Restricted Cash at End of Period	246.0	379.0	556.5
Parent Company
OPERATING ACTIVITIES
Net Income	2,967.1	2,208.1	2,307.2
Adjustments to Reconcile Net Income to Net Cash Flows from Operating Activities:
Depreciation and Amortization	0.6	0.5	0.4
Amortization of KPCo Basis Difference	(21.4)	(16.5)	0.0
Deferred Income Taxes	(53.3)	59.7	(63.3)
Loss on the Expected Sale of the Kentucky Operations	0.0	0.0	363.3
Equity Earnings of Unconsolidated Subsidiaries	(3,280.2)	(2,468.2)	(2,809.6)
Cash Dividends Received from Unconsolidated Subsidiaries	1,143.4	686.3	603.9
Change in Other Noncurrent Assets	4.9	(28.4)	(5.0)
Change in Other Noncurrent Liabilities	70.8	92.3	83.5
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	17.9	28.7	(61.0)
Accounts Payable	(16.5)	(15.9)	1.1
Other Current Assets	0.0	(3.6)	(6.0)
Other Current Liabilities	55.3	(14.5)	(76.6)
Net Cash Flows from Operating Activities	888.6	528.5	337.9
INVESTING ACTIVITIES
Construction Expenditures	(0.6)	(0.8)	(0.7)
Change in Advances to Affiliates, Net	59.9	2,007.6	(1,411.3)
Capital Contributions to Unconsolidated Subsidiaries	(399.9)	(789.9)	(568.3)
Return of Capital Contributions from Unconsolidated Subsidiaries	898.9	56.6	24.5
Issuance of Notes Receivable to Unconsolidated Subsidiaries	0.0	(210.0)	(20.0)
Repayment of Notes Receivable from Unconsolidated Subsidiaries	190.0	0.0	0.0
Other Investing Activities	0.0	0.0	(0.2)
Net Cash Flows Used for Investing Activities	748.3	1,063.5	(1,976.0)
FINANCING ACTIVITIES
Issuance of Common Stock, Net	552.1	999.6	826.5
Issuance of Long-term Debt	1,285.4	1,829.8	986.6
Issuance of Short-term Debt with Original Maturities greater than 90 Days	723.8	1,069.9	833.9
Change in Short-term Debt with Original Maturities less than 90 Day, Net	(172.3)	(1,365.4)	1,650.4
Retirement of Long-term Debt	(1,104.0)	(1,050.0)	(300.0)
Change in Advances from Affiliates, Net	(221.7)	(191.6)	336.9
Redemption of Short-term Debt with Original Maturities greater than 90 Days	(871.1)	(1,128.8)	(986.1)
Dividends Paid on Common Stock	(1,898.3)	(1,752.3)	(1,628.7)
Other Financing Activities	(41.1)	(59.6)	(74.5)
Net Cash Flows from Financing Activities	(1,747.2)	(1,648.4)	1,645.0
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(110.3)	(56.4)	6.9
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	197.8	254.2	247.3
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 87.5	$ 197.8	$ 254.2