Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for uncollectible accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning Of Period	$ 10.5	$ 9.2	$ 6.7
Additions Charged To Costs And Expenses	24.9	27.2	20.7
Additions Charged To Other Accounts	12.5	12.4	16.9
Deductions	28.6	38.3	35.1
Balance At End Of Period	19.3	10.5	9.2
Allowance for uncollectible accounts | Evergy Kansas Central
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning Of Period	3.8	3.9	6.7
Additions Charged To Costs And Expenses	11.1	7.2	9.0
Additions Charged To Other Accounts	2.6	3.4	7.4
Deductions	10.0	10.7	19.2
Balance At End Of Period	7.5	3.8	3.9
Allowance for uncollectible accounts | Evergy Metro
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning Of Period	4.6	3.8	2.2
Additions Charged To Costs And Expenses	9.0	13.7	13.1
Additions Charged To Other Accounts	6.9	6.3	4.4
Deductions	12.4	19.2	15.9
Balance At End Of Period	8.1	4.6	3.8
Tax valuation allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning Of Period	17.5	27.3	0.0
Additions Charged To Costs And Expenses	0.0	0.6	2.2
Additions Charged To Other Accounts	0.0	0.0	26.8
Deductions	3.1	10.4	1.7
Balance At End Of Period	14.4	17.5	27.3
Tax valuation allowance | Evergy Kansas Central
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning Of Period	$ 0.0	1.7	0.0
Additions Charged To Costs And Expenses		0.0	1.7
Additions Charged To Other Accounts		0.0	0.0
Deductions		1.7	0.0
Balance At End Of Period		$ 0.0	$ 1.7