EQUITY BASED COMPENSATION - Remaining Vesting Tranches (Details) - shares	Sep. 30, 2018	Dec. 31, 2017
Equity Incentive Plan Shares
Equity Based Payments
Principal units (in units)	36,002,039	46,422,733
Equity Incentive Plan Shares | October 1, 2018
Equity Based Payments
Principal units (in units)	5,753,904
Equity Incentive Plan Shares | April 1, 2019
Equity Based Payments
Principal units (in units)	9,206,688
Equity Incentive Plan Shares | October 1, 2019
Equity Based Payments
Principal units (in units)	4,471,831
Equity Incentive Plan Shares | April 1, 2020
Equity Based Payments
Principal units (in units)	6,455,250
Equity Incentive Plan Shares | October 1, 2020
Equity Based Payments
Principal units (in units)	3,453,424
Equity Incentive Plan Shares | April 1, 2021
Equity Based Payments
Principal units (in units)	3,337,989
Equity Incentive Plan Shares | October 1, 2021
Equity Based Payments
Principal units (in units)	1,976,345
Equity Incentive Plan Shares | April 1, 2022
Equity Based Payments
Principal units (in units)	118,158
Equity Incentive Plan Shares | October 1, 2022
Equity Based Payments
Principal units (in units)	1,137,278
Equity Incentive Plan Shares | October 1, 2023
Equity Based Payments
Principal units (in units)	91,172
KKR Holdings Principal Awards
Equity Based Payments
Principal units (in units)	26,093,993	30,848,583
KKR Holdings Principal Awards | October 1, 2018
Equity Based Payments
Principal units (in units)	1,970,000
KKR Holdings Principal Awards | April 1, 2019
Equity Based Payments
Principal units (in units)	229,514
KKR Holdings Principal Awards | May 1, 2019
Equity Based Payments
Principal units (in units)	3,680,000
KKR Holdings Principal Awards | October 1, 2019
Equity Based Payments
Principal units (in units)	2,455,000
KKR Holdings Principal Awards | April 1, 2020
Equity Based Payments
Principal units (in units)	124,479
KKR Holdings Principal Awards | May 1, 2020
Equity Based Payments
Principal units (in units)	3,680,000
KKR Holdings Principal Awards | October 1, 2020
Equity Based Payments
Principal units (in units)	2,940,000
KKR Holdings Principal Awards | May 1, 2021
Equity Based Payments
Principal units (in units)	3,680,000
KKR Holdings Principal Awards | October 1, 2021
Equity Based Payments
Principal units (in units)	3,425,000
KKR Holdings Principal Awards | October 1, 2022
Equity Based Payments
Principal units (in units)	3,910,000