DEBT OBLIGATIONS - KKR's Borrowings (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2020 JPY (¥)	Sep. 30, 2020 EUR (€)	Aug. 25, 2020 USD ($)	Apr. 21, 2020 USD ($)	Feb. 25, 2020 USD ($)	Jul. 01, 2019 USD ($)
Debt Instrument [Line Items]
Financing Available	$ 7,920,574,000	$ 6,060,399,000
Borrowing Outstanding	31,451,641,000	27,013,284,000
Fair Value	32,003,292,000	27,379,075,000
Other Debt Obligations
Debt Instrument [Line Items]
Financing Available	5,715,560,000	3,865,495,000
Borrowing Outstanding	25,950,688,000	23,035,991,000
Fair Value	25,943,788,000	23,035,991,000
Senior Notes
Debt Instrument [Line Items]
Borrowing Outstanding	5,500,953,000	3,977,293,000
Fair Value	6,059,504,000	4,343,084,000
Senior Notes | KKR Issued 0.509% Notes Due 2023
Debt Instrument [Line Items]
Borrowing Outstanding	236,006,000	228,280,000
Fair Value	236,769,000	228,026,000
Aggregate principal amount	$ 237,500,000		¥ 25,000,000,000
Interest rate, stated percentage	0.509%		0.509%	0.509%
Unamortized debt issuance costs	$ 700,000	1,000,000.0
Senior Notes | KKR Issued 0.764% Notes Due 2025
Debt Instrument [Line Items]
Borrowing Outstanding	46,840,000	45,255,000
Fair Value	47,635,000	45,856,000
Aggregate principal amount	$ 47,500,000		¥ 5,000,000,000.0
Interest rate, stated percentage	0.764%		0.764%	0.764%
Unamortized debt issuance costs	$ 500,000	600,000
Senior Notes | KKR Issued 1.625% Notes Due 2029
Debt Instrument [Line Items]
Borrowing Outstanding	752,541,000	718,478,000
Fair Value	809,005,000	758,903,000
Aggregate principal amount	$ 760,500,000			€ 650,000,000
Interest rate, stated percentage	1.625%		1.625%	1.625%
Unamortized debt issuance costs	$ 5,300,000	6,300,000
Senior Notes | KKR Issued 3.750% Notes Due 2029
Debt Instrument [Line Items]
Borrowing Outstanding	741,967,000	493,962,000
Fair Value	863,460,000	533,505,000
Aggregate principal amount	$ 750,000,000					$ 250,000,000		$ 500,000,000
Interest rate, stated percentage	3.75%		3.75%	3.75%		3.75%		3.75%
Unamortized debt issuance costs	$ 5,900,000	4,700,000
Senior Notes | KKR Issued 1.595% Notes Due 2038
Debt Instrument [Line Items]
Borrowing Outstanding	96,462,000	93,325,000
Fair Value	102,638,000	98,524,000
Aggregate principal amount	$ 97,900,000		¥ 10,300,000,000
Interest rate, stated percentage	1.595%		1.595%	1.595%
Unamortized debt issuance costs	$ 1,100,000	1,100,000
Senior Notes | KKR Issued 5.500% Notes Due 2043
Debt Instrument [Line Items]
Borrowing Outstanding	492,429,000	492,175,000
Fair Value	636,235,000	613,415,000
Aggregate principal amount	$ 500,000,000
Interest rate, stated percentage	5.50%		5.50%	5.50%
Unamortized debt issuance costs	$ 3,300,000	3,400,000
Senior Notes | KKR Issued 5.125% Notes Due 2044
Debt Instrument [Line Items]
Borrowing Outstanding	991,380,000	991,106,000
Fair Value	1,249,730,000	1,186,670,000
Aggregate principal amount	$ 1,000,000,000.0
Interest rate, stated percentage	5.125%		5.125%	5.125%
Unamortized debt issuance costs	$ 7,400,000	7,700,000
Senior Notes | KKR Issued 3.625% Notes Due 2050
Debt Instrument [Line Items]
Borrowing Outstanding	492,056,000	0
Fair Value	516,180,000	0
Aggregate principal amount	$ 500,000,000						$ 500,000,000
Interest rate, stated percentage	3.625%		3.625%	3.625%			3.625%
Unamortized debt issuance costs	$ 5,400,000
Senior Notes | KKR Issued 3.500% Notes Due 2050
Debt Instrument [Line Items]
Borrowing Outstanding	735,036,000	0
Fair Value	760,508,000	0
Aggregate principal amount	$ 750,000,000				$ 750,000,000
Interest rate, stated percentage	3.50%		3.50%	3.50%	3.50%
Unamortized debt issuance costs	$ 8,200,000
Senior Notes | KFN Issued 5.500% Notes Due 2032 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	494,419,000	494,054,000
Fair Value	496,028,000	504,807,000
Aggregate principal amount	$ 500,000,000.0
Interest rate, stated percentage	5.50%		5.50%	5.50%
Unamortized debt issuance costs	$ 3,800,000	4,000,000.0
Senior Notes | KFN Issued 5.200% Notes Due 2033 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	118,502,000	118,411,000
Fair Value	115,802,000	117,834,000
Aggregate principal amount	$ 120,000,000.0
Interest rate, stated percentage	5.20%		5.20%	5.20%
Unamortized debt issuance costs	$ 1,500,000	1,600,000
Senior Notes | KFN Issued 5.400% Notes Due 2033 | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	68,843,000	68,774,000
Fair Value	68,774,000	70,059,000
Aggregate principal amount	$ 70,000,000.0
Interest rate, stated percentage	5.40%		5.40%	5.40%
Unamortized debt issuance costs	$ 1,200,000	1,200,000
Senior Notes | KFN Issued Junior Subordinated Notes | KFN
Debt Instrument [Line Items]
Borrowing Outstanding	234,472,000	233,473,000
Fair Value	156,740,000	$ 185,485,000
Aggregate principal amount	$ 258,500,000
Weighted average interest rate (percentage)	2.70%	4.40%	2.70%	2.70%
Weighted average remaining maturity (in years)	16 years	16 years 9 months 18 days
Revolving Credit Facility
Debt Instrument [Line Items]
Financing Available	$ 2,205,014,000	$ 2,194,904,000
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	455,014,000	444,904,000
Borrowing Outstanding	0	0
Fair Value	0	0
Revolving Credit Facility | KCM 364-Day Revolving Credit Agreement
Debt Instrument [Line Items]
Financing Available	750,000,000	750,000,000
Borrowing Outstanding	0	0
Fair Value	$ 0	$ 0