PENSION PLANS AND POST-RETIREMENT BENEFITS - Weighted-Average Assumptions (Details)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	3.62%	4.35%
Rate of compensation increase	3.74%	3.76%
Weighted-average assumptions used to determine net costs
Discount rate	4.35%	3.73%
Expected long-term return on plan assets	6.61%	6.52%
Rate of compensation increase	3.76%	3.92%
Post-Retirement Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	3.56%	4.33%
Rate of compensation increase	3.75%	3.50%
Weighted-average assumptions used to determine net costs
Discount rate	4.33%	3.67%
Expected long-term return on plan assets	4.44%	6.00%
Rate of compensation increase	3.50%	3.50%
Evergy Kansas Central \| Pension Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	3.61%	4.35%
Rate of compensation increase	3.78%	4.03%
Weighted-average assumptions used to determine net costs
Discount rate	4.35%	3.73%
Expected long-term return on plan assets	6.75%	6.67%
Rate of compensation increase	4.03%	4.00%
Evergy Kansas Central \| Post-Retirement Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	3.54%	4.33%
Weighted-average assumptions used to determine net costs
Discount rate	4.33%	3.73%
Expected long-term return on plan assets	6.00%	6.00%
Evergy Metro Inc \| Pension Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	3.64%	4.36%
Rate of compensation increase	3.71%	3.64%
Weighted-average assumptions used to determine net costs
Discount rate	4.36%	3.72%
Expected long-term return on plan assets	6.47%	6.46%
Rate of compensation increase	3.64%	3.62%
Evergy Metro Inc \| Post-Retirement Benefits
Weighted-average assumptions used to determine the benefit obligation
Discount rate	3.58%	4.33%
Rate of compensation increase	3.75%	3.50%
Weighted-average assumptions used to determine net costs
Discount rate	4.33%	3.64%
Expected long-term return on plan assets	2.94%	2.80%
Rate of compensation increase	3.50%	3.50%

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(1)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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- Definition

Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

+ References

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- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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- Definition

Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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