DEBT OBLIGATIONS - KKR's Borrowings (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 31, 2018 JPY (¥)	Feb. 12, 2018 USD ($)
Debt Instrument [Line Items]
Financing Available	$ 3,878,646,000	$ 4,293,752,000
Borrowing Outstanding	22,041,271,000	21,193,859,000
Fair Value	22,192,164,000	21,427,594,000
Fund Financing Facilities and Other
Debt Instrument [Line Items]
Financing Available	1,676,423,000	2,056,096,000
Borrowing Outstanding	3,584,588,000	2,898,215,000
Fair Value	$ 3,584,588,000	$ 2,898,215,000
Weighted average interest rate (percentage)	4.30%	4.20%	4.30%
Weighted average remaining maturity (in years)	3 years 3 months 18 days	3 years 7 months 6 days
Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 15,251,646,000
Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount	379,260,000		¥ 40,300,000,000
Senior Notes | KKR Issued 6.375% Notes Due 2020
Debt Instrument [Line Items]
Borrowing Outstanding	498,536,000	$ 498,390,000
Fair Value	540,275,000	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	491,581,000	491,496,000
Fair Value	545,730,000	580,000,000
Aggregate principal amount	$ 500,000,000
Interest rate, stated percentage	5.50%		5.50%
Unamortized debt issuance costs	$ 3,700,000	3,700,000
Senior Notes | KKR Issued 5.125% Notes Due 2044
Debt Instrument [Line Items]
Borrowing Outstanding	990,466,000	990,375,000
Fair Value	1,036,910,000	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	234,004,000	0
Fair Value	235,247,000	0
Aggregate principal amount	$ 235,272,500.0		¥ 25,000,000,000
Interest rate, stated percentage	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	46,488,000	0
Fair Value	47,052,000	0
Aggregate principal amount	$ 47,054,500.0		¥ 5,000,000,000
Interest rate, stated percentage	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	95,921,000	0
Fair Value	97,227,000	0
Aggregate principal amount	$ 96,932,270.00		¥ 10,300,000,000
Interest rate, stated percentage	1.595%		1.595%
Unamortized debt issuance costs	$ 1,000,000
Senior Notes | KFN Issued 5.500% Notes Due 2032 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	493,249,000	493,129,000
Fair Value	523,647,000	505,235,000
Aggregate principal amount	$ 500,000,000.0
Interest rate, stated percentage	5.50%		5.50%
Unamortized debt issuance costs	$ 4,600,000	4,700,000
Senior Notes | KFN Issued 5.200% Notes Due 2033 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	118,407,000	0
Fair Value	122,169,000	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	$ 1,600,000
Senior Notes | KFN Issued Junior Subordinated Notes | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	236,385,000	236,038,000
Fair Value	207,673,000	$ 201,828,000
Aggregate principal amount	$ 264,800,000
Weighted average interest rate (percentage)	4.20%	3.80%	4.20%
Weighted average remaining maturity (in years)	18 years 6 months	19 years 11 days
Senior Secured Notes | Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 9,806,031,000	$ 10,055,686,000
Fair Value	$ 9,806,031,000	10,055,686,000
Weighted average interest rate (percentage)	2.80%		2.80%
Weighted average remaining maturity (in years)	11 years 9 months 18 days
Subordinated Notes | Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 307,448,000	292,294,000
Fair Value	$ 307,448,000	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	$ 5,138,167,000	5,238,236,000
Fair Value	5,138,167,000	5,238,236,000
Collateralized Mortgage Backed Securities | Debt Obligations of Consolidated CFEs
Debt Instrument [Line Items]
Borrowing Outstanding	$ 5,138,167,000
Weighted average interest rate (percentage)	4.40%		4.40%
Weighted average remaining maturity (in years)	26 years 4 months 24 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	452,223,000	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