EQUITY BASED COMPENSATION - Narrative (Details) $ / shares in Units, $ in Millions		1 Months Ended		9 Months Ended
	Nov. 02, 2017 $ / shares shares	Nov. 30, 2016 USD ($)	Feb. 29, 2016 shares	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 shares
KKR Group Partnerships
Equity Based Payments
Percentage owned by KKR Holdings L.P.				36.60%	41.80%
KKR Holdings Principal Awards
Equity Based Payments
Vesting period (in years)		5 years
Minimum transfer restriction period with respect to one-half awards vested (in years)				1 year
Portion of awards vested having one-year transfer restriction period (as a percent)				50.00%
Minimum transfer restriction period with respect to remaining one-half awards vested (in years)				2 years
Portion of awards vested having two-year transfer restriction period (as a percent)				50.00%
Minimum retained ownership required to continuously hold common share equivalents to as percentage of cumulatively vested interests				25.00%
Percentage of outstanding units not granted (less than)				0.20%
Forfeiture rate assumed (as a percent)				7.00%
Estimated unrecognized equity-based payment expense | $		$ 320.9		$ 281.7
Weighted average remaining vesting period over which unvested shares are expected to vest (in years) (less than 1 year for equity based awards)				2 years
Common units conversion basis				1
Number of common units owned in KKR Group Partnership Units (in units) | shares				303,106,993	339,845,707
Modified awards granted (in units) | shares			28,900,000
KKR Holdings Principal Awards | Minimum
Equity Based Payments
Vesting period (in years)				3 years
KKR Holdings Principal Awards | Maximum
Equity Based Payments
Vesting period (in years)				5 years
Equity Incentive Plan Shares
Equity Based Payments
Total awards issuable as a percentage of diluted common units outstanding				15.00%
Minimum retained ownership required to continuously hold common share equivalents to as percentage of cumulatively vested interests				15.00%
Forfeiture rate assumed (as a percent)				7.00%
Estimated unrecognized equity-based payment expense | $				$ 380.7
Weighted average remaining vesting period over which unvested shares are expected to vest (in years) (less than 1 year for equity based awards)				1 year 3 months 4 days
Equity Incentive Plan Shares | Minimum
Equity Based Payments
Vesting period (in years)				3 years
Equity Incentive Plan Shares | Maximum
Equity Based Payments
Vesting period (in years)				5 years
Equity Incentive Plan Shares | Market Condition Awards
Equity Based Payments
Awards granted per individual (in shares) | shares	2,500,000
Performance condition, closing market price (in dollars per share) | $ / shares	$ 40
Required term of performance condition	10 days
Fair value of award at grant date (in dollars per share) | $ / shares	$ 4.02
Compensation expense recognition period				3 years
Estimated unrecognized equity-based payment expense | $				$ 14.0
Equity Incentive Plan Shares | KKR Holdings
Equity Based Payments
Minimum transfer restriction period with respect to one-half awards vested (in years)				1 year
Portion of awards vested having one-year transfer restriction period (as a percent)				50.00%
Minimum transfer restriction period with respect to remaining one-half awards vested (in years)				2 years
Portion of awards vested having two-year transfer restriction period (as a percent)				50.00%