KW UNSECURED DEBT - Borrowings Under Credit Facilities (Details)		12 Months Ended
	Oct. 20, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Repayment of lines of credit		$ 200,000,000.0	$ 450,000,000.0	$ 500,000,000.0
Revolving Credit Facility [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Debt, net of discount (premium)		0	$ 75,000,000.0
A&R Facility [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity and debt instrument, face amount		700,000,000
A&R Facility [Member] | Term Loan [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 200,000,000
A&R Facility [Member] | Term Loan [Member] | LIBOR [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate (as percent)		1.65%
A&R Facility [Member] | Term Loan [Member] | LIBOR [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate (as percent)		2.65%
A&R Facility [Member] | Revolving Credit Facility [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 500,000,000
Maturity of extension		1 year
Maximum consolidated leverage ratio	65.00%
Fixed charge coverage ratio measurement period	12 months
Covenant, percent of new equity offerings	50.00%
Maximum secured recourse leverage multiplier	1.5
Proceeds from issuance of debt		$ 125,000,000.0
Repayments of debt		200,000,000.0
Repayment of lines of credit		125,000,000.0
Maximum amount outstanding during period		150,000,000.0
Remaining borrowing capacity		$ 500,000,000.0
A&R Facility [Member] | Revolving Credit Facility [Member] | Line of Credit [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Fixed charge coverage ratio	1.70
Tangible net worth	$ 1,066,775,300
Liquidity	$ 75,000,000.0
A&R Facility [Member] | Revolving Credit Facility [Member] | Line of Credit [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Secured recourse leverage ratio	3.50%
Liquidity	$ 300,351,000
Adjusted secured leverage ratio	55.00%
A&R Facility [Member] | Revolving Credit Facility [Member] | Line of Credit [Member] | LIBOR [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate (as percent)		1.75%
A&R Facility [Member] | Revolving Credit Facility [Member] | Line of Credit [Member] | LIBOR [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate (as percent)		2.75%
A&R Facility [Member] | Revolving Credit Facility [Member] | Term Loan [Member]
Line of Credit Facility [Line Items]
Repayments of term loan		$ 75,000,000.0
KW Revolving Facility [Member] | Revolving Credit Facility [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Average outstanding amount		$ 93,000,000.0