CONSOLIDATED STATEMENTS OF ASSETS AND LIABILITIES (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Real estate properties at cost	$ 14,226.1	$ 14,163.2
Real estate joint ventures at cost	5,505.6	5,497.9
Real estate funds at cost	696.7	692.9
Real estate operating business at cost	352.5	251.6
Marketable securities at cost	2,579.1	2,217.0
Loans receivable at cost	1,270.0	1,434.3
Loans receivable with related parties at cost	69.8	69.8
Total investments at cost	24,699.8	24,326.7
Loans payable principal outstanding	$ 2,323.8	$ 2,362.6