Investments in Real Estate - Acquisitions Allocation (Details) £ in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)	Mar. 31, 2022 GBP (£)	Mar. 31, 2021 USD ($)	Mar. 31, 2021 GBP (£)
Acquisitions
Weighted average amortization period for acquired lease intangible assets	10 years 9 months 18 days	10 years 9 months 18 days	16 years 9 months 18 days	16 years 9 months 18 days
Weighted average amortization period for acquired lease intangible liabilities	10 years 3 months 18 days	10 years 3 months 18 days	11 years 10 months 24 days	11 years 10 months 24 days
Real Estate Investment | U.S.
Acquisitions
Land	$ 203.5		$ 208.0
Buildings and improvements	368.5		295.8
Lease intangible assets	59.0		94.5
Other assets	117.8		16.7
Lease intangible liabilities	(8.4)		(1.4)
Other liabilities	(12.5)		(21.6)
Net	727.9		$ 592.0
Allocated to other assets, financing receivables with above-market terms	99.6
Allocated to other assets, finance lease right-of-use assets	$ 18.2
Real Estate Investment | U.K.
Acquisitions
Land | £		£ 208,700		£ 117,300
Buildings and improvements | £		237,100		129,000
Lease intangible assets | £		96,500		44,800
Other assets | £		98,300		0
Lease intangible liabilities | £		(46,400)		(900)
Other liabilities | £		0		0
Net | £		£ 594,200		290,200
Allocated to land, right of use assets under long-term ground leases | £				£ 560