Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating activities
Net income	$ 1,409.7	$ 1,298.5	$ 1,201.4
Reconciliation to cash provided by operating activities
Depreciation and amortization	1,122.6	1,074.3	975.9
Deferred income taxes and ITCs, net	280.1	151.1	209.4
Contributions and payments related to pension and OPEB plans	(15.1)	(66.3)	(113.2)
Equity income in transmission affiliates, net of distributions	(74.3)	(25.1)	(29.1)
Net change in transmission regulatory assets and liabilities	(85.8)	5.7	36.2
Net gain on disposition of assets	(66.2)	(6.2)	(3.5)
Change in -
Accounts receivable and unbilled revenues, net	(342.1)	(249.2)	16.1
Materials, supplies, and inventories	(171.3)	(107.2)	21.2
Amounts recoverable from customers	60.0	(82.3)	0.9
Collateral on deposit	(108.1)	4.6	15.6
Other current assets	(27.7)	17.6	(3.1)
Accounts payable	121.5	126.9	(61.3)
Other current liabilities	126.9	(17.2)	(41.2)
Other, net	(169.5)	(92.5)	(29.3)
Net cash provided by operating activities	2,060.7	2,032.7	2,196.0
Investing Activities
Capital expenditures	(2,314.9)	(2,252.8)	(2,238.8)
Acquisition of Thunderhead, net of cash acquired of $0.5	(382.0)	0.0	0.0
Acquisition of Jayhawk	0.0	(119.9)	0.0
Acquisition of Blooming Grove, net of restricted cash acquired of $24.1	0.0	0.0	(364.6)
Acquisition of Tatanka Ridge	0.0	0.0	(239.9)
Acquisition of intangible assets	(19.2)	0.0	0.0
Capital contributions to transmission affiliates	(45.5)	0.0	(21.2)
Proceeds from the sale of assets	69.0	21.9	20.3
Proceeds from the sale of investments held in rabbi trust	15.4	18.7	56.2
Purchase of investments held in rabbi trust	0.0	0.0	(37.8)
Payments for ATC's construction costs that will be reimbursed	(24.8)	(7.0)	(3.5)
Reimbursement for ATC's construction costs	10.2	0.0	1.1
Insurance proceeds received for property damage	41.6	0.0	23.2
Other, net	7.8	27.3	(1.8)
Net cash used in investing activities	(2,642.4)	(2,311.8)	(2,806.8)
Financing Activities
Exercise of stock options	33.6	15.7	43.8
Purchase of common stock	(69.2)	(33.1)	(99.2)
Dividends paid on common stock	(917.9)	(854.8)	(798.0)
Issuance of long-term debt	1,999.3	2,383.8	2,373.6
Retirement of long-term debt	(92.1)	(1,260.4)	(1,767.0)
Issuance of short-term loan	2.7	0.9	340.0
Repayment of short-term loan	0.0	(340.0)	0.0
Change in commercial paper	(252.6)	459.2	606.1
Payments for debt extinguishment and issuance costs	(15.6)	(67.2)	(55.8)
Purchase of additional ownership interest in Upstream from noncontrolling interest	0.0	0.0	(31.0)
Other, net	(11.8)	(10.1)	(11.4)
Net cash provided by financing activities	676.4	294.0	601.1
Net change in cash, cash equivalents, and restricted cash	94.7	14.9	(9.7)
Cash, cash equivalents, and restricted cash at beginning of year	87.5	72.6	82.3
Cash, cash equivalents, and restricted cash at end of year	$ 182.2	$ 87.5	$ 72.6