ORGANIZATION AND BASIS OF PRESENTATION - New Accounting Pronouncements (Details) - ASU 2016-02 $ in Millions	Jan. 01, 2019 USD ($)
Entity Information [Line Items]
Lease asset	$ 110
Lease liability	110
Westar Energy
Entity Information [Line Items]
Lease asset	40
Lease liability	40
KCP&L
Entity Information [Line Items]
Lease asset	80
Lease liability	$ 80