Schedule IV - Changes in Carrying Amount of Mortgage Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Mortgage Loans On Real Estate [Abstract]
Beginning balance	$ 33,519	$ 32,366	$ 32,737
New mortgage loans	1,734	4,287	1,505
Loan repayments	(3,771)	(2,368)	(1,227)
Collection of principal	(627)	(766)	(649)
Ending balance	$ 30,855	$ 33,519	$ 32,366