FAIR VALUE MEASUREMENTS - Recurring (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions | Sep. 30, 2019 | Dec. 31, 2018 |
Assets | | |
Total nuclear decommissioning trust | $ 541 | $ 472.1 |
Total rabbi trust | 45.6 | 43.8 |
Total self-insured health plan trust | 10.3 | 12.4 |
Total Assets | 596.9 | 528.3 |
Liabilities | | |
Total | | 5.4 |
Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 5.4 |
Level 1 | | |
Assets | | |
Total nuclear decommissioning trust | 461.2 | 396 |
Total rabbi trust | 0.7 | 0.2 |
Total self-insured health plan trust | 5.5 | 8.8 |
Total Assets | 467.4 | 405 |
Liabilities | | |
Total | | 0 |
Level 1 | Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 0 |
Level 2 | | |
Assets | | |
Total nuclear decommissioning trust | 36.1 | 33.5 |
Total rabbi trust | 0 | 0 |
Total self-insured health plan trust | 4.8 | 3.6 |
Total Assets | 40.9 | 37.1 |
Liabilities | | |
Total | | 5.4 |
Level 2 | Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 5.4 |
Level 3 | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Total self-insured health plan trust | 0 | 0 |
Total Assets | 0 | 0 |
Liabilities | | |
Total | | 0 |
Level 3 | Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 0 |
NAV | | |
Assets | | |
Total nuclear decommissioning trust | 43.7 | 42.6 |
Total rabbi trust | 44.9 | 43.6 |
Total self-insured health plan trust | 0 | 0 |
Total Assets | 88.6 | 86.2 |
Liabilities | | |
Total | | 0 |
NAV | Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 0 |
Evergy Kansas Central Inc [Member] | | |
Assets | | |
Total nuclear decommissioning trust | 258.5 | 227.5 |
Total rabbi trust | 31.8 | 30.6 |
Total Assets | 290.3 | 258.1 |
Evergy Kansas Central Inc [Member] | Core bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 36.6 | 37.5 |
Total rabbi trust | 25.5 | 24.8 |
Evergy Kansas Central Inc [Member] | High-yield bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 21.3 | 18.9 |
Evergy Kansas Central Inc [Member] | Emerging markets bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 17.2 | 15.4 |
Evergy Kansas Central Inc [Member] | Combination debt/equity/other fund | | |
Assets | | |
Total nuclear decommissioning trust | 15.4 | 12.9 |
Total rabbi trust | 6.1 | 5.6 |
Evergy Kansas Central Inc [Member] | Alternative investments fund | | |
Assets | | |
Total nuclear decommissioning trust | 24.8 | 24.1 |
Evergy Kansas Central Inc [Member] | Real estate securities fund | | |
Assets | | |
Total nuclear decommissioning trust | 12.4 | 11.8 |
Evergy Kansas Central Inc [Member] | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 0.1 | 0.1 |
Total rabbi trust | 0.2 | 0.2 |
Evergy Kansas Central Inc [Member] | Level 1 | | |
Assets | | |
Total nuclear decommissioning trust | 214.8 | 184.9 |
Total rabbi trust | 0.2 | 0.2 |
Total Assets | 215 | 185.1 |
Evergy Kansas Central Inc [Member] | Level 1 | Core bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 36.6 | 37.5 |
Total rabbi trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 1 | High-yield bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 21.3 | 18.9 |
Evergy Kansas Central Inc [Member] | Level 1 | Emerging markets bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 17.2 | 15.4 |
Evergy Kansas Central Inc [Member] | Level 1 | Combination debt/equity/other fund | | |
Assets | | |
Total nuclear decommissioning trust | 15.4 | 12.9 |
Total rabbi trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 1 | Alternative investments fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 1 | Real estate securities fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 1 | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 0.1 | 0.1 |
Total rabbi trust | 0.2 | 0.2 |
Evergy Kansas Central Inc [Member] | Level 2 | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Total Assets | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 2 | Core bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 2 | High-yield bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 2 | Emerging markets bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 2 | Combination debt/equity/other fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 2 | Alternative investments fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 2 | Real estate securities fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 2 | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 3 | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Total Assets | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 3 | Core bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 3 | High-yield bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 3 | Emerging markets bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 3 | Combination debt/equity/other fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 3 | Alternative investments fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 3 | Real estate securities fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Level 3 | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | NAV | | |
Assets | | |
Total nuclear decommissioning trust | 43.7 | 42.6 |
Total rabbi trust | 31.6 | 30.4 |
Total Assets | 75.3 | 73 |
Evergy Kansas Central Inc [Member] | NAV | Core bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 25.5 | 24.8 |
Evergy Kansas Central Inc [Member] | NAV | High-yield bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | NAV | Emerging markets bond fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | NAV | Combination debt/equity/other fund | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 6.1 | 5.6 |
Evergy Kansas Central Inc [Member] | NAV | Alternative investments fund | | |
Assets | | |
Total nuclear decommissioning trust | 24.8 | 24.1 |
Evergy Kansas Central Inc [Member] | NAV | Real estate securities fund | | |
Assets | | |
Total nuclear decommissioning trust | 12.4 | 11.8 |
Evergy Kansas Central Inc [Member] | NAV | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total rabbi trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Domestic | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 84 | 70.6 |
Evergy Kansas Central Inc [Member] | Domestic | Level 1 | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 77.5 | 63.9 |
Evergy Kansas Central Inc [Member] | Domestic | Level 2 | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Domestic | Level 3 | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | Domestic | NAV | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 6.5 | 6.7 |
Evergy Kansas Central Inc [Member] | International | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 46.7 | 36.2 |
Evergy Kansas Central Inc [Member] | International | Level 1 | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 46.7 | 36.2 |
Evergy Kansas Central Inc [Member] | International | Level 2 | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | International | Level 3 | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Kansas Central Inc [Member] | International | NAV | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | | |
Assets | | |
Total nuclear decommissioning trust | 282.5 | 244.6 |
Total self-insured health plan trust | 10.3 | 12.4 |
Total Assets | 292.8 | 257 |
Evergy Metro Inc [Member] | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 193.7 | 166.6 |
Total self-insured health plan trust | 0.5 | 0.5 |
Evergy Metro Inc [Member] | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 2.6 | 1.7 |
Evergy Metro Inc [Member] | U.S. Treasury | | |
Assets | | |
Total nuclear decommissioning trust | 50.1 | 42.1 |
Evergy Metro Inc [Member] | U.S. Agency | | |
Assets | | |
Total nuclear decommissioning trust | 0.4 | 0.4 |
Evergy Metro Inc [Member] | State and local obligations | | |
Assets | | |
Total nuclear decommissioning trust | 2.2 | 2.1 |
Evergy Metro Inc [Member] | Corporate bonds | | |
Assets | | |
Total nuclear decommissioning trust | 33 | 30.9 |
Evergy Metro Inc [Member] | Foreign governments | | |
Assets | | |
Total nuclear decommissioning trust | 0.1 | 0.1 |
Evergy Metro Inc [Member] | Other | | |
Assets | | |
Total nuclear decommissioning trust | 0.4 | 0.7 |
Evergy Metro Inc [Member] | Debt securities | | |
Assets | | |
Total self-insured health plan trust | 6.1 | 3.9 |
Evergy Metro Inc [Member] | Cash and cash equivalents | | |
Assets | | |
Total self-insured health plan trust | 3.7 | 8 |
Evergy Metro Inc [Member] | Level 1 | | |
Assets | | |
Total nuclear decommissioning trust | 246.4 | 211.1 |
Total self-insured health plan trust | 5.5 | 8.8 |
Total Assets | 251.9 | 219.9 |
Evergy Metro Inc [Member] | Level 1 | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 193.7 | 166.6 |
Total self-insured health plan trust | 0.5 | 0.5 |
Evergy Metro Inc [Member] | Level 1 | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 2.6 | 1.7 |
Evergy Metro Inc [Member] | Level 1 | U.S. Treasury | | |
Assets | | |
Total nuclear decommissioning trust | 50.1 | 42.1 |
Evergy Metro Inc [Member] | Level 1 | U.S. Agency | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 1 | State and local obligations | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 1 | Corporate bonds | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 1 | Foreign governments | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 1 | Other | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0.7 |
Evergy Metro Inc [Member] | Level 1 | Debt securities | | |
Assets | | |
Total self-insured health plan trust | 1.3 | 0.3 |
Evergy Metro Inc [Member] | Level 1 | Cash and cash equivalents | | |
Assets | | |
Total self-insured health plan trust | 3.7 | 8 |
Evergy Metro Inc [Member] | Level 2 | | |
Assets | | |
Total nuclear decommissioning trust | 36.1 | 33.5 |
Total self-insured health plan trust | 4.8 | 3.6 |
Total Assets | 40.9 | 37.1 |
Evergy Metro Inc [Member] | Level 2 | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total self-insured health plan trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 2 | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 2 | U.S. Treasury | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 2 | U.S. Agency | | |
Assets | | |
Total nuclear decommissioning trust | 0.4 | 0.4 |
Evergy Metro Inc [Member] | Level 2 | State and local obligations | | |
Assets | | |
Total nuclear decommissioning trust | 2.2 | 2.1 |
Evergy Metro Inc [Member] | Level 2 | Corporate bonds | | |
Assets | | |
Total nuclear decommissioning trust | 33 | 30.9 |
Evergy Metro Inc [Member] | Level 2 | Foreign governments | | |
Assets | | |
Total nuclear decommissioning trust | 0.1 | 0.1 |
Evergy Metro Inc [Member] | Level 2 | Other | | |
Assets | | |
Total nuclear decommissioning trust | 0.4 | 0 |
Evergy Metro Inc [Member] | Level 2 | Debt securities | | |
Assets | | |
Total self-insured health plan trust | 4.8 | 3.6 |
Evergy Metro Inc [Member] | Level 2 | Cash and cash equivalents | | |
Assets | | |
Total self-insured health plan trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total self-insured health plan trust | 0 | 0 |
Total Assets | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total self-insured health plan trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | U.S. Treasury | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | U.S. Agency | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | State and local obligations | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | Corporate bonds | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | Foreign governments | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | Other | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | Debt securities | | |
Assets | | |
Total self-insured health plan trust | 0 | 0 |
Evergy Metro Inc [Member] | Level 3 | Cash and cash equivalents | | |
Assets | | |
Total self-insured health plan trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total self-insured health plan trust | 0 | 0 |
Total Assets | 0 | 0 |
Evergy Metro Inc [Member] | NAV | Equity securities | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Total self-insured health plan trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | Cash equivalents | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | U.S. Treasury | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | U.S. Agency | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | State and local obligations | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | Corporate bonds | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | Foreign governments | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | Other | | |
Assets | | |
Total nuclear decommissioning trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | Debt securities | | |
Assets | | |
Total self-insured health plan trust | 0 | 0 |
Evergy Metro Inc [Member] | NAV | Cash and cash equivalents | | |
Assets | | |
Total self-insured health plan trust | 0 | 0 |
Other Evergy | | |
Assets | | |
Total rabbi trust | 13.8 | 13.2 |
Liabilities | | |
Total | | 5.4 |
Other Evergy | Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 5.4 |
Other Evergy | Cash and cash equivalents | | |
Assets | | |
Total rabbi trust | 0.5 | |
Other Evergy | Fixed income fund | | |
Assets | | |
Total rabbi trust | 13.3 | 13.2 |
Other Evergy | Level 1 | | |
Assets | | |
Total rabbi trust | 0.5 | 0 |
Liabilities | | |
Total | | 0 |
Other Evergy | Level 1 | Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 0 |
Other Evergy | Level 1 | Cash and cash equivalents | | |
Assets | | |
Total rabbi trust | 0.5 | |
Other Evergy | Level 1 | Fixed income fund | | |
Assets | | |
Total rabbi trust | 0 | 0 |
Other Evergy | Level 2 | | |
Assets | | |
Total rabbi trust | 0 | 0 |
Liabilities | | |
Total | | 5.4 |
Other Evergy | Level 2 | Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 5.4 |
Other Evergy | Level 2 | Cash and cash equivalents | | |
Assets | | |
Total rabbi trust | 0 | |
Other Evergy | Level 2 | Fixed income fund | | |
Assets | | |
Total rabbi trust | 0 | 0 |
Other Evergy | Level 3 | | |
Assets | | |
Total rabbi trust | 0 | 0 |
Liabilities | | |
Total | | 0 |
Other Evergy | Level 3 | Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 0 |
Other Evergy | Level 3 | Cash and cash equivalents | | |
Assets | | |
Total rabbi trust | 0 | |
Other Evergy | Level 3 | Fixed income fund | | |
Assets | | |
Total rabbi trust | 0 | 0 |
Other Evergy | NAV | | |
Assets | | |
Total rabbi trust | 13.3 | 13.2 |
Liabilities | | |
Total | | 0 |
Other Evergy | NAV | Interest rate swaps | | |
Liabilities | | |
Interest rate swaps | | 0 |
Other Evergy | NAV | Cash and cash equivalents | | |
Assets | | |
Total rabbi trust | 0 | |
Other Evergy | NAV | Fixed income fund | | |
Assets | | |
Total rabbi trust | $ 13.3 | $ 13.2 |