Real Estate and Other Activities - Net Assets Acquired (Parenthetical) (Detail) $ in Thousands, £ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021 USD ($) Property	Sep. 30, 2021 GBP (£) Property
Business Acquisition [Line Items]
Advanced to the mortgage loan | $		$ 1,090,400
Priory Group [Member]
Business Acquisition [Line Items]
Number of real estate assets acquired | Property		35	35
Mortgage Loans [Member] | Priory Group [Member]
Business Acquisition [Line Items]
Advanced to the mortgage loan | £			£ 800
Intangible Lease Assets [Member]
Business Acquisition [Line Items]
Weighted-average useful life of acquired intangible lease assets (in years)	20 years 4 months 24 days	36 years 1 month 6 days