Schedule IV: Mortgage Loans on Real Estate - Reconciliation of Mortgage Loans (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance at beginning of year	$ 42,037	$ 161,964	$ 42,037	$ 188,418
New mortgage loans	0	98,469	59,552
Draws on existing mortgage loans	42,398	19,182	60,375
Total additions	42,398	117,651	119,927
Principal repayments and conversions to equity ownership	(188,779)	(113,200)	0
Reserve for loan losses(2)		(8,843)	0	0
Total deductions	$ (188,779)	(122,043)	0
Balance at end of year		$ 157,572	$ 161,964	$ 42,037