EQUITY BASED COMPENSATION - Estimated Unrecognized Expense (Details) - USD ($) $ in Millions	Sep. 30, 2018	Nov. 30, 2016
Equity Incentive Plan Shares
Equity Based Payments
Estimated unrecognized equity-based payment expense	$ 380.7
Equity Incentive Plan Shares | Remainder of 2018
Equity Based Payments
Estimated unrecognized equity-based payment expense	48.9
Equity Incentive Plan Shares | 2019
Equity Based Payments
Estimated unrecognized equity-based payment expense	167.9
Equity Incentive Plan Shares | 2020
Equity Based Payments
Estimated unrecognized equity-based payment expense	112.8
Equity Incentive Plan Shares | 2021
Equity Based Payments
Estimated unrecognized equity-based payment expense	39.2
Equity Incentive Plan Shares | 2022
Equity Based Payments
Estimated unrecognized equity-based payment expense	11.0
Equity Incentive Plan Shares | 2023
Equity Based Payments
Estimated unrecognized equity-based payment expense	0.9
KKR Holdings Principal Awards
Equity Based Payments
Estimated unrecognized equity-based payment expense	281.7	$ 320.9
KKR Holdings Principal Awards | Remainder of 2018
Equity Based Payments
Estimated unrecognized equity-based payment expense	25.0
KKR Holdings Principal Awards | 2019
Equity Based Payments
Estimated unrecognized equity-based payment expense	96.1
KKR Holdings Principal Awards | 2020
Equity Based Payments
Estimated unrecognized equity-based payment expense	87.9
KKR Holdings Principal Awards | 2021
Equity Based Payments
Estimated unrecognized equity-based payment expense	47.4
KKR Holdings Principal Awards | 2022
Equity Based Payments
Estimated unrecognized equity-based payment expense	$ 25.3