LOANS (Details 2) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Corporate loans
Net realized and unrealized (losses) gains
Credit risk gain	$ 23,500	$ 170,200	$ 29,000	$ 197,700
Corporate loans, at estimated fair value
Net realized and unrealized (losses) gains
Net realized gains (losses)	(30,490)	(180,238)	(34,376)	(210,952)
Net (increase) decrease in unrealized losses	17,877	190,503	15,991	235,426
Net realized and unrealized gains (losses)	$ (12,613)	$ 10,265	$ (18,385)	$ 24,474

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding loans and leases.

No definition available.

+ Details

Name:	kfn_LoansAndLeasesReceivableGainLoss
Namespace Prefix:	kfn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate net change in the difference between the fair value and the carrying value, or in the comparative fair values, of loans and leases.

+ References

No definition available.

+ Details

Name:	kfn_LoansAndLeasesReceivableUnrealizedGainLoss
Namespace Prefix:	kfn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the estimated amount of gains or losses included in earnings during the period attributable to changes in instrument-specific credit risk arising from loans and other receivables held as assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612

+ Details

Name:	us-gaap_FairValueOptionCreditRiskGainsLossesOnAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The gains (losses) included in earnings that represent the difference between the sale price and the carrying value of loans and leases that were sold during the reporting period. This element refers to the gain (loss) and not to the cash proceeds of the sales. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3521-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainLossOnSaleOfLoansAndLeases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_GainLossOnSaleOfLoansAndLeasesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_LoansReceivableMember
Namespace Prefix:
Data Type:	na
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Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=kfn_CorporateLoansAtEstimatedFairValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: