Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net income	$ 1,298.5	$ 1,201.4	$ 1,134.7
Reconciliation to cash provided by operating activities
Depreciation and amortization	1,074.3	975.9	926.3
Deferred income taxes and ITCs, net	151.1	209.4	162.9
Contributions and payments related to pension and OPEB plans	(66.3)	(113.2)	(65.9)
Equity income in transmission affiliates, net of distributions	(25.1)	(29.1)	(2.9)
Change in -
Accounts receivable and unbilled revenues, net	(249.2)	16.1	98.2
Materials, supplies, and inventories	(107.2)	21.2	(1.5)
Amounts recoverable from customers	(82.3)	0.9	29.8
Other current assets	22.2	12.5	(36.9)
Accounts payable	126.9	(61.3)	1.5
Other current liabilities	(17.2)	(41.2)	78.7
Other, net	(93.0)	3.4	20.6
Net cash provided by operating activities	2,032.7	2,196.0	2,345.5
Investing Activities
Capital expenditures	(2,252.8)	(2,238.8)	(2,260.8)
Acquisition of Jayhawk	(119.9)	0.0	0.0
Acquisition of Blooming Grove, net of restricted cash acquired of $24.1	0.0	(364.6)	0.0
Acquisition of Tatanka Ridge	0.0	(239.9)	0.0
Acquisition of Upstream, net of cash and restricted cash acquired of $9.2	0.0	0.0	(268.2)
Capital contributions to transmission affiliates	0.0	(21.2)	(52.6)
Proceeds from the sale of assets and businesses	21.9	20.3	37.6
Proceeds from the sale of investments held in rabbi trust	18.7	56.2	0.2
Purchase of investments held in rabbi trust	0.0	(37.8)	0.0
Reimbursement for ATC's construction costs	0.0	1.1	32.4
Insurance proceeds received for property damage	0.0	23.2	0.0
Other, net	20.3	(5.3)	16.5
Net cash used in investing activities	(2,311.8)	(2,806.8)	(2,494.9)
Financing Activities
Exercise of stock options	15.7	43.8	67.0
Purchase of common stock	(33.1)	(99.2)	(140.1)
Dividends paid on common stock	(854.8)	(798.0)	(744.5)
Issuance of long-term debt	2,383.8	2,373.6	1,895.0
Retirement of long-term debt	(1,260.4)	(1,767.0)	(360.1)
Issuance of short-term loan	0.9	340.0	0.0
Repayment of short-term loan	(340.0)	0.0	0.0
Change in other-short-term debt	459.2	606.1	(609.3)
Payments for debt extinguishment and issuance costs	(67.2)	(55.8)	(12.5)
Purchase of additional ownership interest in Upstream from noncontrolling interest	0.0	(31.0)	0.0
Other, net	(10.1)	(11.4)	(9.9)
Net cash provided by financing activities	294.0	601.1	85.6
Net change in cash, cash equivalents, and restricted cash	14.9	(9.7)	(63.8)
Cash, cash equivalents, and restricted cash at beginning of year	72.6	82.3	146.1
Cash, cash equivalents, and restricted cash at end of year	$ 87.5	$ 72.6	$ 82.3