DEBT OBLIGATIONS - KKR's Borrowings (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2018 JPY (¥)	May 23, 2018 USD ($)	Mar. 23, 2018 JPY (¥)	Feb. 12, 2018 USD ($)
Debt Instrument [Line Items]
Financing Available	$ 3,927,775,000	$ 4,293,752,000
Borrowing Outstanding	19,972,383,000	21,193,859,000
Fair Value	20,064,742,000	21,427,594,000
Fund Financing Facilities and Other
Debt Instrument [Line Items]
Financing Available	1,726,052,000	2,056,096,000
Borrowing Outstanding	4,109,911,000	2,898,215,000
Fair Value	$ 4,109,911,000	$ 2,898,215,000
Weighted average interest rate (percentage)	4.60%	4.20%	4.60%
Weighted average remaining maturity (in years)	3 years 4 months 24 days	3 years 7 months 6 days
Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 12,608,642,000
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	498,682,000	$ 498,390,000
Fair Value	532,755,000	549,000,000
Aggregate principal amount	$ 500,000,000
Interest rate, stated percentage	6.375%		6.375%
Unamortized debt issuance costs	$ 900,000	1,000,000
Senior Notes | KKR Issued 5.500% Notes Due 2043
Debt Instrument [Line Items]
Borrowing Outstanding	491,667,000	491,496,000
Fair Value	527,405,000	580,000,000
Aggregate principal amount	$ 500,000,000
Interest rate, stated percentage	5.50%		5.50%
Unamortized debt issuance costs	$ 3,600,000	3,700,000
Senior Notes | KKR Issued 5.125% Notes Due 2044
Debt Instrument [Line Items]
Borrowing Outstanding	990,557,000	990,375,000
Fair Value	1,017,580,000	1,107,100,000
Aggregate principal amount	$ 1,000,000,000.0
Interest rate, stated percentage	5.125%		5.125%
Unamortized debt issuance costs	$ 8,200,000	8,300,000
Senior Notes | KKR Issued 0.509% Notes Due 2023
Debt Instrument [Line Items]
Borrowing Outstanding	224,693,000	0
Fair Value	225,723,000	0
Aggregate principal amount	$ 225,989,000		¥ 25,000,000,000		¥ 25,000,000,000
Interest rate, stated percentage	0.509%		0.509%		0.509%
Unamortized debt issuance costs	$ 1,300,000
Senior Notes | KKR Issued 0.764% Notes Due 2025
Debt Instrument [Line Items]
Borrowing Outstanding	44,556,000	0
Fair Value	45,139,000	0
Aggregate principal amount	$ 45,198,000		¥ 5,000,000,000		¥ 5,000,000,000
Interest rate, stated percentage	0.764%		0.764%		0.764%
Unamortized debt issuance costs	$ 600,000
Senior Notes | KKR Issued 1.595% Notes Due 2038
Debt Instrument [Line Items]
Borrowing Outstanding	92,013,000	0
Fair Value	93,379,000	0
Aggregate principal amount	$ 93,107,000		¥ 10,300,000,000.0		¥ 10,300,000,000
Interest rate, stated percentage	1.595%		1.595%		1.595%
Unamortized debt issuance costs	$ 1,100,000
Senior Notes | KFN Issued 5.500% Notes Due 2032 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	493,325,000	493,129,000
Fair Value	506,454,000	505,235,000
Aggregate principal amount	$ 500,000,000.0
Interest rate, stated percentage	5.50%		5.50%
Unamortized debt issuance costs	$ 4,500,000	4,700,000
Senior Notes | KFN Issued 5.200% Notes Due 2033 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	118,230,000	0
Fair Value	117,980,000	0
Aggregate principal amount	$ 120,000,000					$ 120,000,000.0
Interest rate, stated percentage	5.20%		5.20%			5.20%
Unamortized debt issuance costs	$ 1,800,000
Senior Notes | KFN Issued 5.400% Notes Due 2033 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	68,636,000	0
Fair Value	70,248,000	0
Aggregate principal amount	$ 70,000,000			$ 70,000,000.0
Interest rate, stated percentage	5.40%		5.40%	5.40%
Unamortized debt issuance costs	$ 1,400,000
Senior Notes | KFN Issued Junior Subordinated Notes | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	231,471,000	236,038,000
Fair Value	209,526,000	$ 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 3 months 18 days	19 years 11 days
Senior Secured Notes | Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 11,127,365,000	$ 10,055,686,000
Fair Value	$ 11,127,365,000	10,055,686,000
Weighted average interest rate (percentage)	3.20%		3.20%
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	$ 389,931,000	292,294,000
Fair Value	$ 389,931,000	292,294,000
Weighted average remaining maturity (in years)	12 years 1 month 6 days
Collateralized Mortgage Backed Securities
Debt Instrument [Line Items]
Borrowing Outstanding	$ 1,091,346,000	5,238,236,000
Fair Value	1,091,346,000	5,238,236,000
Collateralized Mortgage Backed Securities | Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 1,091,346,000
Weighted average interest rate (percentage)	4.00%		4.00%
Weighted average remaining maturity (in years)	30 years 3 months 18 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