Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income	$ 685.6	$ 546.0	$ 336.5
Adjustments to reconcile income to net cash from operating activities:
Depreciation and amortization	861.7	618.8	371.7
Amortization of nuclear fuel	51.4	43.6	32.2
Amortization of deferred refueling outage	25.5	21.2	16.1
Amortization of corporate-owned life insurance	19.8	22.6	20.6
Non-cash compensation	16.3	29.9	8.8
Net deferred income taxes and credits	121.5	124.2	149.6
Allowance for equity funds used during construction	(2.2)	(3.1)	(2.0)
Payments for asset retirement obligations	(17.8)	(22.4)	(16.0)
Equity in earnings of equity method investees, net of income taxes	(9.8)	(5.4)	(6.7)
Income from corporate-owned life insurance	(29.6)	(2.3)	(2.8)
Other	(3.2)	(5.2)	(8.7)
Changes in working capital items:
Accounts receivable from subsidiaries	(23.1)	265.1	(2.1)
Accounts receivable pledged as collateral	26.0	(185.0)	0.0
Fuel inventory and supplies	29.9	54.7	7.2
Prepaid expenses and other current assets	43.4	(128.1)	55.8
Accounts payable	16.9	56.7	10.0
Accrued taxes	(8.2)	(76.4)	9.2
Other current liabilities	(59.4)	92.0	(118.0)
Changes in other assets	79.8	66.8	32.0
Changes in other liabilities	(75.5)	(15.9)	19.3
Cash Flows from Operating Activities	1,749.0	1,497.8	912.7
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Additions to property, plant and equipment	(1,210.1)	(1,069.7)	(764.6)
Cash acquired from the merger with Great Plains Energy	0.0	1,154.2	0.0
Purchase of securities - trusts	(55.8)	(117.5)	(41.0)
Sale of securities - trusts	47.3	117.7	41.2
Investment in corporate-owned life insurance	(18.3)	(17.1)	(17.0)
Proceeds from investment in corporate-owned life insurance	161.7	6.8	4.2
Proceeds from settlement of interest rate swap	0.0	140.6	0.0
Other investing activities	(5.1)	(17.6)	(3.6)
Cash Flows from (used in) Investing Activities	(1,080.3)	197.4	(780.8)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Short term debt, net	(176.7)	(104.0)	(91.3)
Proceeds from term loan facility	1,000.0	0.0	0.0
Repayment of term loan facility	(1,000.0)	0.0	0.0
Collateralized short-term borrowings, net	(26.0)	185.0	0.0
Proceeds from long-term debt	2,372.7	290.9	296.2
Retirements of long-term debt	(701.1)	(395.8)	(125.0)
Retirements of long-term debt of variable interest entities	(30.3)	(28.5)	(26.8)
Payment for settlement of interest rate swap accounted for as a cash flow hedge	(69.8)	0.0	0.0
Borrowings against cash surrender value of corporate-owned life insurance	59.4	56.5	55.1
Repayment of borrowings against cash surrender value of corporate-owned life insurance	(127.5)	(3.9)	(1.0)
Cash dividends paid	(462.5)	(475.0)	(223.1)
Repurchase of common stock under repurchase plan	(1,628.7)	(1,042.3)	0.0
Distributions to shareholders of noncontrolling interests	(8.6)	0.0	(5.8)
Other financing activities	(6.7)	(21.3)	(9.9)
Cash Flows from (used in) Financing Activities	(805.8)	(1,538.4)	(131.6)
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(137.1)	156.8	0.3
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
Beginning of period	160.3	3.5	3.2
End of period	$ 23.2	$ 160.3	$ 3.5