Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating activities
Net income	$ 1,524.3	$ 1,331.7	$ 1,409.7
Reconciliation to cash provided by operating activities
Depreciation and amortization	1,354.5	1,264.2	1,122.6
Deferred income taxes and ITCs, net	529.0	219.4	280.1
Impairment related to ICC disallowances	12.1	178.9	0.0
Contributions and payments related to pension and OPEB plans	(14.5)	(16.7)	(15.1)
Equity income in transmission affiliates, net of distributions	(57.4)	(33.0)	(74.3)
Net change in transmission regulatory assets and liabilities	(22.8)	19.8	(85.8)
Net loss (gain) on disposition of assets	0.7	(23.8)	(66.2)
Change in -
Accounts receivable and unbilled revenues, net	(161.5)	340.6	(342.1)
Materials, supplies, and inventories	(38.0)	41.9	(171.3)
Collateral on deposit	84.3	22.1	(108.1)
Other current assets	(75.4)	36.3	32.3
Accounts payable	99.7	(254.0)	121.5
Other current liabilities	11.6	47.5	126.9
Other, net	(34.8)	(156.5)	(169.5)
Net cash provided by operating activities	3,211.8	3,018.4	2,060.7
Investing activities
Capital expenditures	(2,781.1)	(2,492.9)	(2,314.9)
Acquisition of Delilah I, net of cash acquired of $0.6	(462.5)	0.0	0.0
Acquisition of Maple Flats, net of cash acquired of $0.5	(431.2)	0.0	0.0
Acquisition of West Riverside	(97.9)	(95.3)	0.0
Acquisition of Red Barn	(2.1)	(143.8)	0.0
Acquisition of Whitewater	0.0	(76.0)	0.0
Acquisition of Sapphire Sky, net of cash acquired of $0.3	0.0	(442.6)	0.0
Acquisition of Samson I, net of cash acquired of $5.2	0.0	(257.3)	0.0
Acquisition of Thunderhead, net of cash acquired of $0.5	0.0	0.0	(382.0)
Capital contributions to transmission affiliates	(45.5)	(63.7)	(45.5)
Proceeds from the sale of assets	1.7	32.8	69.0
Insurance proceeds received for property damage	6.0	2.5	41.6
Other, net	10.1	(21.9)	(10.6)
Net cash used in investing activities	(3,802.5)	(3,558.2)	(2,642.4)
Financing activities
Exercise of stock options	23.7	6.3	33.6
Issuance of common stock, net	163.4	0.0	0.0
Purchase of common stock	(3.2)	(16.6)	(69.2)
Dividends paid on common stock	(1,056.2)	(984.2)	(917.9)
Issuance of long-term debt	4,460.9	2,170.0	1,999.3
Retirement of long-term debt	(2,138.0)	(1,005.4)	(92.1)
Change in commercial paper	(902.8)	373.7	(252.6)
Purchase of additional ownership interest in Samson I from noncontrolling interest	(28.1)	0.0	0.0
Payments for debt extinguishment and issuance costs	(45.9)	(14.2)	(15.6)
Other, net	(6.1)	(6.8)	(9.1)
Net cash provided by financing activities	467.7	522.8	676.4
Net change in cash, cash equivalents, and restricted cash	(123.0)	(17.0)	94.7
Cash, cash equivalents, and restricted cash at beginning of year	165.2	182.2	87.5
Cash, cash equivalents, and restricted cash at end of year	$ 42.2	$ 165.2	$ 182.2