Schedule IV - Changes in Mortgage Loans Excluding Unamortized Loan Issue Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Mortgage Loans On Real Estate [Abstract]
Balance at beginning of year	$ 1,274,995	$ 1,213,283	$ 1,778,264
New mortgage loans and additional advances on existing loans	193,590	61,712	50,783
Exchange rate fluctuations	9,785
Mortgage loans on real estate including additions during year	1,478,370	1,274,995	1,829,047
Collection of principal	(1,230,035)		(615,764)
Deductions during year	(1,230,035)		(615,764)
Balance at end of year	$ 248,335	$ 1,274,995	$ 1,213,283