KWE Unsecured Bonds - Schedule of KWE Unsecured Bonds (Details) - KWE Unsecured Bonds [Member] - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total debt	$ 1,217.4	$ 1,274.2
KWE [Member]
Debt Instrument [Line Items]
Mortgage debt (excluding loan fees)	1,220.4	1,277.6
Unamortized loan fees	(3.0)	(3.4)
Total debt	1,217.4	1,274.2
Unamortized discount (premium)	(2.9)	(3.1)
KWE [Member] \| KWE Bonds [Member]
Debt Instrument [Line Items]
Mortgage debt (excluding loan fees)	619.8	662.9
KWE [Member] \| KWE Euro Medium Term Note Programme [Member]
Debt Instrument [Line Items]
Mortgage debt (excluding loan fees)	$ 600.6	$ 614.7

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