PENSION PLANS AND POST-RETIREMENT BENEFITS - Weighted-Average Assumptions (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	2.95%	3.62%
Rate of compensation increase	3.71%	3.74%
Interest crediting rate for cash balance plans	4.12%	4.32%
Weighted-average assumptions used to determine net costs
Discount rate	3.62%	4.35%
Expected long-term return on plan assets	6.63%	6.61%
Rate of compensation increase	3.74%	3.76%
Interest crediting rate for cash balance plans	4.32%	4.32%
Post-Retirement Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	2.84%	3.56%
Rate of compensation increase	3.75%	3.75%
Weighted-average assumptions used to determine net costs
Discount rate	3.56%	4.33%
Expected long-term return on plan assets	4.19%	4.44%
Rate of compensation increase	3.75%	3.50%
Evergy Kansas Central | Pension Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	2.93%	3.61%
Rate of compensation increase	3.76%	3.78%
Interest crediting rate for cash balance plans	4.00%	4.21%
Weighted-average assumptions used to determine net costs
Discount rate	3.61%	4.35%
Expected long-term return on plan assets	6.70%	6.75%
Rate of compensation increase	3.75%	4.03%
Interest crediting rate for cash balance plans	4.21%	4.21%
Evergy Kansas Central | Post-Retirement Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	2.80%	3.54%
Weighted-average assumptions used to determine net costs
Discount rate	3.54%	4.33%
Expected long-term return on plan assets	6.00%	6.00%
Evergy Metro | Pension Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	2.97%	3.64%
Rate of compensation increase	3.71%	3.71%
Interest crediting rate for cash balance plans	4.46%	4.50%
Weighted-average assumptions used to determine net costs
Discount rate	3.64%	4.36%
Expected long-term return on plan assets	6.56%	6.47%
Rate of compensation increase	3.71%	3.64%
Interest crediting rate for cash balance plans	4.50%	4.50%
Evergy Metro | Post-Retirement Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	2.88%	3.58%
Rate of compensation increase	3.75%	3.75%
Weighted-average assumptions used to determine net costs
Discount rate	3.58%	4.33%
Expected long-term return on plan assets	2.37%	2.94%
Rate of compensation increase	3.75%	3.50%