Real Estate and Other Activities - Alecto Facilities - Additional Information (Detail) - Alecto Healthcare Services [Member] $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2022 USD ($) Property	Dec. 31, 2021 Lease
Business Acquisition [Line Items]
Number of leased properties \| Property	4
Number of properties sold \| Lease		3
Proceeds from sale of mortgage loans \| $	$ 51
Total Gross Assets [Member] \| Customer Concentration Risk [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Percentage of total assets	0.10%

The cash inflow from sales of loans that are secured with real estate mortgages and are held with the intention to resell in the near future.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3461-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3536-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration