Concentrations of Risk - Schedule of diversification of the Account's portfolio by region and property type (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Concentration Risk [Line Items]
Concentration risk percentage	100.00%	100.00%
Office
Concentration Risk [Line Items]
Concentration risk percentage	37.20%
Apartment
Concentration Risk [Line Items]
Concentration risk percentage	25.70%
Retail
Concentration Risk [Line Items]
Concentration risk percentage	19.60%
Industrial
Concentration Risk [Line Items]
Concentration risk percentage	15.80%
Other
Concentration Risk [Line Items]
Concentration risk percentage	1.70%
West
Concentration Risk [Line Items]
Concentration risk percentage	39.70%
West | Office
Concentration Risk [Line Items]
Concentration risk percentage	13.20%
West | Apartment
Concentration Risk [Line Items]
Concentration risk percentage	10.00%
West | Retail
Concentration Risk [Line Items]
Concentration risk percentage	6.80%
West | Industrial
Concentration Risk [Line Items]
Concentration risk percentage	9.10%
West | Other
Concentration Risk [Line Items]
Concentration risk percentage	0.60%
East
Concentration Risk [Line Items]
Concentration risk percentage	31.30%
East | Office
Concentration Risk [Line Items]
Concentration risk percentage	18.70%
East | Apartment
Concentration Risk [Line Items]
Concentration risk percentage	6.60%
East | Retail
Concentration Risk [Line Items]
Concentration risk percentage	3.90%
East | Industrial
Concentration Risk [Line Items]
Concentration risk percentage	1.60%
East | Other
Concentration Risk [Line Items]
Concentration risk percentage	0.50%
South
Concentration Risk [Line Items]
Concentration risk percentage	26.60%
South | Office
Concentration Risk [Line Items]
Concentration risk percentage	5.30%
South | Apartment
Concentration Risk [Line Items]
Concentration risk percentage	8.10%
South | Retail
Concentration Risk [Line Items]
Concentration risk percentage	8.00%
South | Industrial
Concentration Risk [Line Items]
Concentration risk percentage	4.60%
South | Other
Concentration Risk [Line Items]
Concentration risk percentage	0.60%
Midwest
Concentration Risk [Line Items]
Concentration risk percentage	2.40%
Midwest | Office
Concentration Risk [Line Items]
Concentration risk percentage	0.00%
Midwest | Apartment
Concentration Risk [Line Items]
Concentration risk percentage	1.00%
Midwest | Retail
Concentration Risk [Line Items]
Concentration risk percentage	0.90%
Midwest | Industrial
Concentration Risk [Line Items]
Concentration risk percentage	0.50%
Midwest | Other
Concentration Risk [Line Items]
Concentration risk percentage	0.00%