Changes in Mortgage Loans (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Mortgage Loans On Real Estate [Abstract]
Balance at beginning of period	$ 120,130
Additions during period:
Interest	12,150
Deductions during period:
Provision for loan loss reserve	(19,393)
Collections of principal and interest	(112,887)
Balance at close of period	$ 0