Other Assets - Schedule of Other Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Other Assets [Abstract]
Hedge assets	$ 53.0	$ 32.6
Straight line rent receivable	48.2	47.3
Loan purchases and originations	16.0	29.4
Deferred taxes, net	24.2	24.4
Goodwill	23.9	23.9
Right of use asset, net	12.5	13.6	$ 12.5
Prepaid expenses	13.3	14.3
Leasing commissions, net of accumulated amortization of $4.9 and $4.7 at March 31, 2020 and December 31, 2019, respectively	11.9	11.9
Other, net of accumulated amortization of $2.1 and $2.0 at March 31, 2020 and December 31, 2019, respectively	17.6	16.5
Other Assets	262.6	263.7
Accumulated amortization, other	2.1	2.0
Accumulated amortization, leasing commissions	4.9	4.7
Furniture and Fixtures [Member]
Other Assets [Abstract]
Furniture and equipment net of accumulated depreciation of $21.3 and $21.9 at March 31, 2020 and December 31, 2019, respectively	21.8	23.7
Accumulated amortization, office furniture and equipment	21.3	21.9
Above Market Leases [Member]
Other Assets [Abstract]
Above-market leases, net of accumulated amortization of $50.4 and $51.0 at March 31, 2020 and December 31, 2019, respectively	20.2	26.1
Accumulated amortization, above-market leases	$ 50.4	$ 51.0