Loans Receivable - Schedule of fair values and risk ratings (Details) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2022	Sep. 30, 2022 USD ($) loan	Dec. 31, 2021 USD ($) loan
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		33	31
Fair Value | $		$ 1,548.5	$ 1,492.6
Related Party
Financing Receivable, Credit Quality Indicator [Line Items]
Number of loans collateralized by equity interests in real estate investments		3	3
Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value	100.00%	100.00%	100.00%
AA
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		0	1
Fair Value | $		$ 0.0	$ 62.6
AA | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		0.00%	4.20%
AA-
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		0	0
Fair Value | $		$ 0.0	$ 0.0
AA- | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		0.00%	0.00%
A
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		3	4
Fair Value | $		$ 180.7	$ 248.5
A | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		11.70%	16.60%
A-
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		1	0
Fair Value | $		$ 46.3	$ 0.0
A- | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		3.00%	0.00%
BBB+
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		3	0
Fair Value | $		$ 192.3	$ 0.0
BBB+ | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		12.40%	0.00%
BBB
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		2	6
Fair Value | $		$ 134.8	$ 374.7
BBB | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		8.70%	25.10%
BBB-
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		0	0
Fair Value | $		$ 0.0	$ 0.0
BBB- | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		0.00%	0.00%
BB+
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		3	0
Fair Value | $		$ 122.8	$ 0.0
BB+ | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		7.90%	0.00%
BB
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		3	10
Fair Value | $		$ 82.2	$ 437.8
BB | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		5.30%	29.30%
BB-
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		1	0
Fair Value | $		$ 19.5	$ 0.0
BB- | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		1.30%	0.00%
B+
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		3	0
Fair Value | $		$ 97.5	$ 0.0
B+ | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		6.30%	0.00%
B
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		1	5
Fair Value | $		$ 58.0	$ 144.3
B | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		3.80%	9.70%
B-
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		4	0
Fair Value | $		$ 207.1	$ 0.0
B- | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		13.40%	0.00%
CCC+
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		1	0
Fair Value | $		$ 40.6	$ 0.0
CCC+ | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		2.60%	0.00%
CCC
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		2	0
Fair Value | $		$ 127.4	$ 0.0
CCC | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		8.20%	0.00%
CCC-
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		1	0
Fair Value | $		$ 80.3	$ 0.0
CCC- | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		5.20%	0.00%
C
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		1	2
Fair Value | $		$ 79.1	$ 154.8
C | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		5.10%	10.40%
D
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		1	0
Fair Value | $		$ 10.0	$ 0.0
D | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		0.60%	0.00%
NR
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans		3	3
Fair Value | $		$ 69.9	$ 69.9
NR | Loans Receivable | Credit Concentration Risk
Financing Receivable, Credit Quality Indicator [Line Items]
% of Fair Value		4.50%	4.70%