LEASES - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 22.2	$ 21.7
Operating cash flows from finance leases	2.8	2.8
Financing cash flows from finance leases	5.6	5.0
Right-of-use assets obtained in exchange for new operating lease liabilities	6.9	10.4
Right-of-use assets obtained in exchange for new finance lease liabilities	5.6	8.3
Evergy Kansas Central
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	12.9	13.7
Operating cash flows from finance leases	2.5	2.6
Financing cash flows from finance leases	5.1	4.8
Right-of-use assets obtained in exchange for new operating lease liabilities	6.6	6.1
Right-of-use assets obtained in exchange for new finance lease liabilities	4.0	8.3
Evergy Metro
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	10.8	9.9
Operating cash flows from finance leases	0.1	0.1
Financing cash flows from finance leases	0.4	0.1
Right-of-use assets obtained in exchange for new operating lease liabilities	0.3	2.4
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 1.6	$ 0.0