Assets and Liabilities Measured at Fair Value on a Recurring Basis - Schedule of fair value assets and liabilities measured on recurring basis using unobservable inputs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total realized and unrealized (losses) gains included in changes in net assets	$ (1,440.5)	$ 1,302.8	$ (2,367.9)	$ 2,692.0
Loans Payable
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(2,129.9)	(2,338.0)	(2,069.7)	(2,380.5)
Total realized and unrealized (losses) gains included in changes in net assets	(15.9)	46.1	(22.7)	49.8
Purchases	(1.1)	(6.1)	(100.0)	(9.1)
Sales	0.0	0.0	0.0	0.0
Settlements	299.6	5.0	345.1	46.8
Ending balance	(1,847.3)	(2,293.0)	(1,847.3)	(2,293.0)
Other Unsecured Debt
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(500.0)	(500.0)	(500.0)	(500.0)
Total realized and unrealized (losses) gains included in changes in net assets	0.0	0.0	0.0	0.0
Purchases	0.0	0.0	0.0	0.0
Sales	0.0	0.0	0.0	0.0
Settlements	0.0	0.0	0.0	0.0
Ending balance	(500.0)	(500.0)	(500.0)	(500.0)
Real Estate Properties
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	20,057.9	20,179.1	20,444.0	18,903.9
Total realized and unrealized (losses) gains included in changes in net assets	(945.4)	977.6	(1,432.8)	2,181.6
Purchases	78.8	308.3	180.1	537.1
Sales	0.0	(176.4)	0.0	(334.0)
Settlements	0.0	0.0	0.0	0.0
Ending balance	19,191.3	21,288.6	19,191.3	21,288.6
Real Estate Joint Ventures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	6,762.1	7,253.3	7,103.6	7,175.9
Total realized and unrealized (losses) gains included in changes in net assets	(350.9)	239.3	(728.2)	362.1
Purchases	55.2	230.4	91.4	481.8
Sales	0.0	0.0	0.0	0.0
Settlements	(124.9)	(80.1)	(125.3)	(376.9)
Ending balance	6,341.5	7,642.9	6,341.5	7,642.9
Real Estate Operating Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	636.0	487.6	641.9	326.3
Total realized and unrealized (losses) gains included in changes in net assets	1.2	140.4	(4.7)	200.8
Purchases	16.4	0.0	16.4	100.9
Sales	0.0	0.0	0.0	0.0
Settlements	0.0	0.0	0.0	0.0
Ending balance	653.6	628.0	653.6	628.0
Loans Receivable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	1,450.2	1,329.2	1,488.6	1,492.6
Total realized and unrealized (losses) gains included in changes in net assets	(116.3)	(83.2)	(159.3)	(82.2)
Purchases	35.1	312.3	47.6	317.5
Sales	0.0	0.0	0.0	(161.4)
Settlements	(3.5)	(0.2)	(11.4)	(8.4)
Ending balance	1,365.5	1,558.1	1,365.5	1,558.1
Total Level 3 Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	28,906.2	29,249.2	29,678.1	27,898.7
Total realized and unrealized (losses) gains included in changes in net assets	(1,411.4)	1,274.1	(2,325.0)	2,662.3
Purchases	185.5	851.0	335.5	1,437.3
Sales	0.0	(176.4)	0.0	(495.4)
Settlements	(128.4)	(80.3)	(136.7)	(385.3)
Ending balance	$ 27,551.9	$ 31,117.6	$ 27,551.9	$ 31,117.6