KWE UNSECURED BONDS - Schedule of KWE Unsecured Bonds (Details) - KWE unsecured bonds [Member] - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Outstanding debt	$ 1,274.2	$ 1,260.5
Unamortized premium (discount)	(3.1)	(3.7)
KWE [Member]
Debt Instrument [Line Items]
Debt, net of discount (premium)	1,277.6	1,264.7
Unamortized loan fees	(3.4)	(4.2)
Outstanding debt	1,274.2	1,260.5
KWE [Member] \| KWE Bonds [Member]
Debt Instrument [Line Items]
Debt, net of discount (premium)	662.9	637.3
KWE [Member] \| KWE Euro Medium Term Note Programme [Member]
Debt Instrument [Line Items]
Debt, net of discount (premium)	$ 614.7	$ 627.4

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