Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
OPERATING REVENUES	$ 5,147.8	$ 4,275.9	$ 2,571.0
OPERATING EXPENSES:
Fuel and purchased power	1,265.0	1,078.7	541.5
SPP network transmission costs	251.3	259.9	247.9
Operating and maintenance	1,218.5	1,115.8	563.5
Depreciation and amortization	861.7	618.8	371.7
Taxes other than income tax	365.5	269.1	167.6
Total Operating Expenses	3,962.0	3,342.3	1,892.2
INCOME FROM OPERATIONS	1,185.8	933.6	678.8
OTHER INCOME (EXPENSE):
Investment earnings	11.0	8.8	4.0
Other income	26.9	15.5	8.3
Other expense	(76.9)	(78.7)	(39.1)
Total Other Expense, Net	(39.0)	(54.4)	(26.8)
Interest expense	374.0	279.6	171.0
INCOME BEFORE INCOME TAXES	772.8	599.6	481.0
Income tax expense	97.0	59.0	151.2
Equity in earnings of equity method investees, net of income taxes	9.8	5.4	6.7
NET INCOME	685.6	546.0	336.5
Less: Net income attributable to noncontrolling interests	15.7	10.2	12.6
Net income attributable to Evergy, Inc.	$ 669.9	$ 535.8	$ 323.9
BASIC AND DILUTED EARNINGS PER AVERAGE COMMON SHARE OUTSTANDING ATTRIBUTABLE TO EVERGY (see Note 1)
Basic earnings per common share (in dollars per share)	$ 2.80	$ 2.50	$ 2.27
Diluted earnings per common share (in dollars per share)	$ 2.79	$ 2.50	$ 2.27
AVERAGE COMMON SHARES OUTSTANDING
Basic (in shares)	239.5	213.9	142.5
Diluted (in shares)	239.9	214.1	142.6
COMPREHENSIVE INCOME
Net income	$ 685.6	$ 546.0	$ 336.5
Derivative hedging activity
Loss on derivative hedging instruments	(64.4)	(5.4)
Loss on derivative hedging instruments			0.0
Income tax benefit	16.5	1.4
Income tax benefit			0.0
Net loss on derivative hedging instruments	(47.9)	(4.0)
Net loss on derivative hedging instruments			0.0
Reclassification to expenses, net of tax	1.5	0.0
Reclassification to expenses, net of tax			0.0
Derivative hedging activity, net of tax	(46.4)	(4.0)
Derivative hedging activity, net of tax			0.0
Defined benefit pension plans
Net gain (loss) arising during period	(0.8)	1.4	0.0
Income tax expense (benefit)	0.2	(0.4)	0.0
Net gain (loss) arising during period	(0.6)	1.0	0.0
Change in unrecognized pension expense, net of tax	(0.6)	1.0	0.0
Total other comprehensive income (loss)	(47.0)	(3.0)	0.0
COMPREHENSIVE INCOME	638.6	543.0	336.5
Less: comprehensive income attributable to noncontrolling interest	15.7	10.2	12.6
COMPREHENSIVE INCOME	$ 622.9	$ 532.8	$ 323.9