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Real Estate and Other Activities - Alecto Facilities - Additional Information (Detail) - Alecto Healthcare Services [Member]
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2021
USD ($)
Property
Mar. 31, 2020
USD ($)
Dec. 31, 2020
Property
Business Acquisition [Line Items]      
Number of leased properties 4    
Number of properties owned 1    
Real estate impairment charge | $   $ 9.1  
Number of re-leased properties     1
Proceeds from sale of mortgage loans | $ $ 51.0    
Total Gross Assets [Member] | Customer Concentration Risk [Member]      
Business Acquisition [Line Items]      
Percentage of total assets 0.10%