Fair Value Measurement (Quantitative Information) (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment in real estate joint ventures and partnerships	$ 25,984
Fair Value, Nonrecurring [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment in real estate joint ventures and partnerships	$ 24,154
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Discount Rate [Member] | Minimum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-financial asset, measurement input	7.30%
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Discount Rate [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-financial asset, measurement input	7.50%
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Cap Rate [Member] | Minimum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-financial asset, measurement input	5.80%
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Cap Rate [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-financial asset, measurement input	8.00%
Valuation Technique, Discounted Cash Flow [Member] | Measurement Input, Discount for Lack of Marketability [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-financial asset, measurement input	15.00%