Fair Value Measurements (Unobervable Quantitative Input Ratios) (Details) - Level 3 - Recurring - Real estate fund investments	Dec. 31, 2019	Dec. 31, 2018
Measurement Input, Discount Rate | Minimum
Unobservable Quantitative Input
Real estate, measurement input	0.082	0.100
Measurement Input, Discount Rate | Maximum
Unobservable Quantitative Input
Real estate, measurement input	0.120	0.150
Measurement Input, Discount Rate | Weighted Average
Unobservable Quantitative Input
Real estate, measurement input	0.093	0.134
Measurement Input, Cap Rate | Minimum
Unobservable Quantitative Input
Real estate, measurement input	0.0460	0.054
Measurement Input, Cap Rate | Maximum
Unobservable Quantitative Input
Real estate, measurement input	0.0820	0.077
Measurement Input, Cap Rate | Weighted Average
Unobservable Quantitative Input
Real estate, measurement input	0.053	0.057