SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Organization (Details) customer in Millions	12 Months Ended
	Dec. 31, 2020 kilovolt_line subsidiary customer mi MW
Summary Of Accounting Policies [Line Items]
Owned generating capacity and renewable purchased power | MW	15,400
Number of customers served | customer	1.6
Prairie Wind Transmission, LLC
Summary Of Accounting Policies [Line Items]
Transmission line length | mi	108
Transmission line electrical potential | kilovolt_line	345
Transource Energy, LLC | Evergy Transmission Company LLC
Summary Of Accounting Policies [Line Items]
Ownership percentage	13.50%
Prairie Wind Transmission, LLC | Evergy Kansas Central
Summary Of Accounting Policies [Line Items]
Ownership percentage	50.00%
Evergy Kansas South Inc | Evergy Kansas Central
Summary Of Accounting Policies [Line Items]
Number of active wholly owned subsidiaries | subsidiary	1
AEP Transmission Holding Company, LLC | Transource Energy, LLC
Summary Of Accounting Policies [Line Items]
Ownership interest	86.50%