Assets and Liabilities Measured at Fair Value on a Recurring Basis - Schedule of unobservable inputs related to Level 3 fair value measurements (Details) - Level 3: Significant Unobservable Inputs	Jun. 30, 2019	Jun. 30, 2018
Discount Rate | Real Estate Properties and Joint Ventures | Office | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.055	0.055
Discount Rate | Real Estate Properties and Joint Ventures | Office | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.086	0.086
Discount Rate | Real Estate Properties and Joint Ventures | Office | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.066	0.066
Discount Rate | Real Estate Properties and Joint Ventures | Industrial | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.053	0.055
Discount Rate | Real Estate Properties and Joint Ventures | Industrial | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.093	0.089
Discount Rate | Real Estate Properties and Joint Ventures | Industrial | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.067	0.068
Discount Rate | Real Estate Properties and Joint Ventures | Apartment | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.055	0.050
Discount Rate | Real Estate Properties and Joint Ventures | Apartment | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.078	0.078
Discount Rate | Real Estate Properties and Joint Ventures | Apartment | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.064	0.062
Discount Rate | Real Estate Properties and Joint Ventures | Retail | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.050	0.050
Discount Rate | Real Estate Properties and Joint Ventures | Retail | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.107	0.110
Discount Rate | Real Estate Properties and Joint Ventures | Retail | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.065	0.064
Capitalization Rate | Real Estate Properties and Joint Ventures | Office | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.040	0.040
Capitalization Rate | Real Estate Properties and Joint Ventures | Office | Minimum | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.035	0.038
Capitalization Rate | Real Estate Properties and Joint Ventures | Office | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.075	0.075
Capitalization Rate | Real Estate Properties and Joint Ventures | Office | Maximum | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.070	0.070
Capitalization Rate | Real Estate Properties and Joint Ventures | Office | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.055	0.055
Capitalization Rate | Real Estate Properties and Joint Ventures | Office | Weighted Average | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.049	0.048
Capitalization Rate | Real Estate Properties and Joint Ventures | Industrial | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.043	0.045
Capitalization Rate | Real Estate Properties and Joint Ventures | Industrial | Minimum | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.039	0.040
Capitalization Rate | Real Estate Properties and Joint Ventures | Industrial | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.083	0.083
Capitalization Rate | Real Estate Properties and Joint Ventures | Industrial | Maximum | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.078	0.075
Capitalization Rate | Real Estate Properties and Joint Ventures | Industrial | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.055	0.055
Capitalization Rate | Real Estate Properties and Joint Ventures | Industrial | Weighted Average | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.049	0.050
Capitalization Rate | Real Estate Properties and Joint Ventures | Apartment | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.038	0.035
Capitalization Rate | Real Estate Properties and Joint Ventures | Apartment | Minimum | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.033	0.033
Capitalization Rate | Real Estate Properties and Joint Ventures | Apartment | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.068	0.063
Capitalization Rate | Real Estate Properties and Joint Ventures | Apartment | Maximum | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.060	0.058
Capitalization Rate | Real Estate Properties and Joint Ventures | Apartment | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.050	0.048
Capitalization Rate | Real Estate Properties and Joint Ventures | Apartment | Weighted Average | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.045	0.043
Capitalization Rate | Real Estate Properties and Joint Ventures | Retail | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.043	0.043
Capitalization Rate | Real Estate Properties and Joint Ventures | Retail | Minimum | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.033	0.038
Capitalization Rate | Real Estate Properties and Joint Ventures | Retail | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.092	0.090
Capitalization Rate | Real Estate Properties and Joint Ventures | Retail | Maximum | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.105	0.100
Capitalization Rate | Real Estate Properties and Joint Ventures | Retail | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.054	0.052
Capitalization Rate | Real Estate Properties and Joint Ventures | Retail | Weighted Average | Direct Capitalization
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Real Estate Properties and Joint Ventures	0.048	0.046
Loan to Value Ratio | Mortgage Loans Payable | Apartment | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.314	0.269
Loan to Value Ratio | Mortgage Loans Payable | Apartment | Minimum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.314	0.269
Loan to Value Ratio | Mortgage Loans Payable | Apartment | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.620	0.639
Loan to Value Ratio | Mortgage Loans Payable | Apartment | Maximum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.620	0.639
Loan to Value Ratio | Mortgage Loans Payable | Apartment | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.481	0.399
Loan to Value Ratio | Mortgage Loans Payable | Apartment | Weighted Average | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.481	0.399
Loan to Value Ratio | Mortgage Loans Payable | Retail | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.320	0.178
Loan to Value Ratio | Mortgage Loans Payable | Retail | Minimum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.320	0.178
Loan to Value Ratio | Mortgage Loans Payable | Retail | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.633	0.567
Loan to Value Ratio | Mortgage Loans Payable | Retail | Maximum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.633	0.567
Loan to Value Ratio | Mortgage Loans Payable | Retail | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.396	0.327
Loan to Value Ratio | Mortgage Loans Payable | Retail | Weighted Average | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.396	0.327
Loan to Value Ratio | Mortgage Loans Payable | Office and Industrial | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.347	0.364
Loan to Value Ratio | Mortgage Loans Payable | Office and Industrial | Minimum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.347	0.364
Loan to Value Ratio | Mortgage Loans Payable | Office and Industrial | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.604	0.687
Loan to Value Ratio | Mortgage Loans Payable | Office and Industrial | Maximum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.604	0.687
Loan to Value Ratio | Mortgage Loans Payable | Office and Industrial | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.473	0.469
Loan to Value Ratio | Mortgage Loans Payable | Office and Industrial | Weighted Average | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.473	0.469
Loan to Value Ratio | Loans Receivable | Office, Retail and Storage | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.693	0.595
Loan to Value Ratio | Loans Receivable | Office, Retail and Storage | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.862	0.775
Loan to Value Ratio | Loans Receivable | Office, Retail and Storage | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.776	0.754
Equivalency Rate | Mortgage Loans Payable | Apartment | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.034	0.034
Equivalency Rate | Mortgage Loans Payable | Apartment | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.040	0.040
Equivalency Rate | Mortgage Loans Payable | Apartment | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.037	0.037
Equivalency Rate | Mortgage Loans Payable | Retail | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.036	0.036
Equivalency Rate | Mortgage Loans Payable | Retail | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.047	0.048
Equivalency Rate | Mortgage Loans Payable | Retail | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.040	0.039
Equivalency Rate | Mortgage Loans Payable | Office and Industrial | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.035	0.039
Equivalency Rate | Mortgage Loans Payable | Office and Industrial | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.055	0.055
Equivalency Rate | Mortgage Loans Payable | Office and Industrial | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	0.040	0.042
Equivalency Rate | Loans Receivable | Office, Retail and Storage | Minimum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.062	0.042
Equivalency Rate | Loans Receivable | Office, Retail and Storage | Maximum | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.087	0.083
Equivalency Rate | Loans Receivable | Office, Retail and Storage | Weighted Average | Discounted Cash Flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans Receivable	0.072	0.064
Weighted Average Cost of Capital Risk Premium Multiple | Mortgage Loans Payable | Apartment | Minimum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.20	1.10
Weighted Average Cost of Capital Risk Premium Multiple | Mortgage Loans Payable | Apartment | Maximum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.40	1.40
Weighted Average Cost of Capital Risk Premium Multiple | Mortgage Loans Payable | Apartment | Weighted Average | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.30	1.30
Weighted Average Cost of Capital Risk Premium Multiple | Mortgage Loans Payable | Retail | Minimum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.20	1.10
Weighted Average Cost of Capital Risk Premium Multiple | Mortgage Loans Payable | Retail | Maximum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.50	1.40
Weighted Average Cost of Capital Risk Premium Multiple | Mortgage Loans Payable | Retail | Weighted Average | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.20	1.20
Weighted Average Cost of Capital Risk Premium Multiple | Mortgage Loans Payable | Office and Industrial | Minimum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.20	1.20
Weighted Average Cost of Capital Risk Premium Multiple | Mortgage Loans Payable | Office and Industrial | Maximum | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.40	1.50
Weighted Average Cost of Capital Risk Premium Multiple | Mortgage Loans Payable | Office and Industrial | Weighted Average | Net Present Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage Loans Payable	1.30	1.30