DEBT OBLIGATIONS - KKR's Borrowings (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2018 JPY (¥)	May 23, 2018 USD ($)	Mar. 23, 2018 JPY (¥)	Feb. 12, 2018 USD ($)
Debt Instrument [Line Items]
Financing Available	$ 5,227,254,000	$ 4,293,752,000
Borrowing Outstanding	20,266,172,000	21,193,859,000
Fair Value	20,300,522,000	21,427,594,000
Financing Facilities of Consolidated Funds and Other
Debt Instrument [Line Items]
Financing Available	3,025,531,000	2,056,096,000
Borrowing Outstanding	4,375,957,000	2,898,215,000
Fair Value	$ 4,375,957,000	$ 2,898,215,000
Weighted average interest rate (percentage)	4.50%	4.20%	4.50%
Weighted average remaining maturity (in years)	3 years	3 years 7 months 6 days
Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 12,645,610,000
Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount | ¥					¥ 40,300,000,000
Senior Notes | KKR Issued 6.375% Notes Due 2020
Debt Instrument [Line Items]
Borrowing Outstanding	498,829,000	$ 498,390,000
Fair Value	525,950,000	549,000,000
Aggregate principal amount	$ 500,000,000
Interest rate, stated percentage	6.375%		6.375%
Debt Issuance Costs, Gross	$ 800,000	1,000,000
Senior Notes | KKR Issued 5.500% Notes Due 2043
Debt Instrument [Line Items]
Borrowing Outstanding	491,751,000	491,496,000
Fair Value	515,480,000	580,000,000
Aggregate principal amount	$ 500,000,000
Interest rate, stated percentage	5.50%		5.50%
Debt Issuance Costs, Gross	$ 3,600,000	3,700,000
Senior Notes | KKR Issued 5.125% Notes Due 2044
Debt Instrument [Line Items]
Borrowing Outstanding	990,648,000	990,375,000
Fair Value	986,610,000	1,107,100,000
Aggregate principal amount	$ 1,000,000,000.0
Interest rate, stated percentage	5.125%		5.125%
Debt Issuance Costs, Gross	$ 8,100,000	8,300,000
Senior Notes | KKR Issued 0.509% Notes Due 2023
Debt Instrument [Line Items]
Borrowing Outstanding	218,562,000	0
Fair Value	219,365,000	0
Aggregate principal amount	$ 219,906,000		¥ 25,000,000,000		¥ 25,000,000,000
Interest rate, stated percentage	0.509%		0.509%		0.509%
Debt Issuance Costs, Gross	$ 1,300,000
Senior Notes | KKR Issued 0.764% Notes Due 2025
Debt Instrument [Line Items]
Borrowing Outstanding	43,243,000	0
Fair Value	43,757,000	0
Aggregate principal amount	$ 43,981,000		¥ 5,000,000,000		¥ 5,000,000,000
Interest rate, stated percentage	0.764%		0.764%		0.764%
Debt Issuance Costs, Gross	$ 700,000
Senior Notes | KKR Issued 1.595% Notes Due 2038
Debt Instrument [Line Items]
Borrowing Outstanding	89,398,000	0
Fair Value	88,632,000	0
Aggregate principal amount	$ 90,601,000		¥ 10,300,000,000.0		¥ 10,300,000,000
Interest rate, stated percentage	1.595%		1.595%		1.595%
Debt Issuance Costs, Gross	$ 1,200,000
Senior Notes | KFN Issued 5.500% Notes Due 2032 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	493,447,000	493,129,000
Fair Value	500,852,000	505,235,000
Aggregate principal amount	$ 500,000,000.0
Interest rate, stated percentage	5.50%		5.50%
Debt Issuance Costs, Gross	$ 4,500,000	4,700,000
Senior Notes | KFN Issued 5.200% Notes Due 2033 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	118,260,000	0
Fair Value	116,657,000	0
Aggregate principal amount	$ 120,000,000					$ 120,000,000.0
Interest rate, stated percentage	5.20%		5.20%			5.20%
Debt Issuance Costs, Gross	$ 1,700,000
Senior Notes | KFN Issued 5.400% Notes Due 2033 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	68,660,000	0
Fair Value	69,426,000	0
Aggregate principal amount	$ 70,000,000			$ 70,000,000.0
Interest rate, stated percentage	5.40%		5.40%	5.40%
Debt Issuance Costs, Gross	$ 1,300,000
Senior Notes | KFN Issued Junior Subordinated Notes | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	231,807,000	236,038,000
Fair Value	212,226,000	$ 201,828,000
Aggregate principal amount	$ 258,500,000
Weighted average interest rate (percentage)	4.80%	3.80%	4.80%
Weighted average remaining maturity (in years)	18 years	19 years 11 days
Senior Secured Notes | Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 11,173,622,000	$ 10,055,686,000
Fair Value	$ 11,173,622,000	10,055,686,000
Weighted average interest rate (percentage)	3.10%		3.10%
Weighted average remaining maturity (in years)	11 years 8 months 12 days
Subordinated Notes | Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 388,881,000	292,294,000
Fair Value	$ 388,881,000	292,294,000
Weighted average remaining maturity (in years)	12 years
Collateralized Mortgage Backed Securities
Debt Instrument [Line Items]
Borrowing Outstanding	$ 1,083,107,000	5,238,236,000
Fair Value	1,083,107,000	5,238,236,000
Collateralized Mortgage Backed Securities | Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 1,083,107,000
Weighted average interest rate (percentage)	4.20%		4.20%
Weighted average remaining maturity (in years)	29 years 8 months 12 days
Revolving Credit Facility | Corporate Credit Agreement
Debt Instrument [Line Items]
Financing Available	$ 1,000,000,000	1,000,000,000
Borrowing Outstanding	0	0
Fair Value	0	0
Revolving Credit Facility | KCM Credit Agreement
Debt Instrument [Line Items]
Financing Available	451,723,000	487,656,000
Borrowing Outstanding	0	0
Fair Value	0	0
Revolving Credit Facility | KCM Short-Term Credit Agreement
Debt Instrument [Line Items]
Financing Available	750,000,000	750,000,000
Borrowing Outstanding	0	0
Fair Value	$ 0	$ 0